Doubting the quick attainments of the Mahasi Tradition

It is unlikely the Mahasi method brings quicker wisdom because the method is based in verbal thought noting. Whatever degree of conceptual thought exists, to that degree the clarity of consciousness available for genuine insight is diminished.

I have noticed that a lot of Mahasi practicers seem to reach sotapanna very quickly.

There is no solid evidence for this. Many of the early practitioners have also switched practice, for more on this see this answer. Also there are other practices like that taught by S.N.Goenka which has been more successful at a mass scale, for more information see this answer.

In addition, the tradition claims being orthodox to Theravada but thought the theoretical aspects of the tradition and the taught the practice diverges from that is in the Pali Canon and Commentaries, which the tradition itself endorse, which lead to an ambiguity or inconsistency as to why not practice what is in the Pali Canon and Commentaries which is accepted and endorsed by the tradition. This effectively translates to "you have to do A" in dhamma talks and "you have to do B" when meditation is taught, which are tangential to the theory in the Talks. Even remote justifications from the Pali Canon, are from more obscure passages then commonly recurring passages.

If this technique is most effective the Buddha would have sensed this and would have trained accordingly. Having said this some practitioners may get results quickly due to perhaps past practice, but I doubt it would be the majority.

What is the difference from other methods of Buddhist Meditation and the Mahasi Method, relative to the apparent speed of attainment in the Mahasi Method?

Some meditation masters advise against mental noting and concentration on the abdomen. More on mental noting see below. On using the abdomen see: What is the Interpretation of Parimukham in the context of Buddhist Meditation?. The practice of Breath Meditation is given in the Anapanasati Sutta and the practice of this tradition is tangential to the technique in the Sutta.

Maybe you think Mahasi style practice does not lead to these better results?

If so, who, what, where, when and why do you think this?

The benefit of mental noting is getting concentrated and reducing the chance of uncontrolled mental proliferation (verbalisation and sub verbalisation in a way can be considered mental proliferation abide with some control), at the expense of creating verbal fabrication, nutriment (ahara), concepts (pannatti), which are dealt with in more detail in this answer, this answer, this answer, this answer, and this answer. When verbally noting in the spear of concepts and perceptions than the ultimate realities of deep insights. In the abdomen method you trade deeper concentration for ease of practice, where easy may not be as effective. Also for the ease of practice the method advocates staying with the more grosses sensation than reaching the important stration of feeling the whole body. For more information see: How is the Pali Phase "Sabbakayapatisamvedi Assasissami... passasissamiti sikkhati..." Interpreted as per Different Linage?. Also misconception about emphasising walking meditation as required, than being an aid to avoid sleepiness, see this answer and this answer.

Some masters to not make these compromises which can have a negative effect on progress.

To help get an understanding into who, what, where, when and why about Mahasi Sayadaw, I started to read “Practical Vipassana Meditation Exercises, by Mahasi Sayadaw: Part 1, Basic Practice. It was interesting to note that nowhere in that whole document any reference being made to the Scriptures (the Suttas). If there were any, @Uuu, even you would have found out for yourself what I came to know of him and his “meditation instructors”. Be it Mahasi, his ‘instructors, you or any one of us in this Group, we can only be 'DISCIPLES' of the Supreme Buddha. And nothing more. If we follow the scriptures (original Suttas & Vinaya) to the letter, we can be guides to others. In this document Mahasi never defined WHAT a Sotapanna / Stream Entry is, and HOW a Stream Entry occur.

In his reply to the OP How does stream entry occur? @yuttadhammo (Ven.) answered this clearly, and precisely. He took the Rathavinita Sutta (The only sutta that fully explains the seven purifications) to explain the road to become a Sotapanna. This Sutta explains in full the seven purifications (SAPTHA VISUDDHI) taught by the Buddha. The Ratha-vinita Sutta: Relay Chariots (MN 24; M.I,145) To fully explain each of these seven purifications would require a separate OP for each.

I took the Thayodhamma sutta(Abandon three things at a time)...... to explain the skills that should be developed to achieve this supreme task.

The Sotāpanna attains an intuitive grasp of Dhamma (right view) and has complete confidence in the Three Jewels (Buddha, Dhamma, and Sangha) WHEN the Sotapanna have "opened the eye of the Dhamma" (dhamma chakkhu), because he has realized that whatever arises, will cease. (impermanence). His conviction in the true Dhamma is unshakable. Instead of these three supreme protections - The Three Jewels (Buddha, Dhamma, and Sangha) – Mahasi talks about “Four Protections”. This is the first time that I came across such. I have read but a very few suttas. So if someone could refer me to where these “Four Protections” came from I’ll be thankful. The Three Jewels are mentioned in the Dhajagga Sutta. Taking refuge in the 3 jewels of Buddha, Dhamma and Sangha was recommended by the Buddha as providing protection from afflictions. It is specifically mentioned in the **Dhajagga-paritta ("Banner Protection") - SN 11.3.

@Uuu, please compare Mahasi’s explanation of the nine supreme qualities of the Buddha and my reply to the OP Why worship Buddha?. Mahasi describes Lokavidû as “World Knower”. I have explained this fifth quality “Lokavidu” to mean ‘knower of the three worlds’ – the Human, the Deva, & the Brahma, and as It is one who understands the origin of all worlds, understands the cessation of all worlds, and understands how to escape from all the three worlds.

I can go on and on and on in comparing Mahasi Sayadaw’s article to the Scriptures, but I do not want to. It should be clear to you by now, that WHERE those who fall into such trappings will go NO-WHERE. Let us now analyze our lives. By not realizing the truth, we have travelled this long and sorrowful cycle of birth and death, with great suffering and pain. Due to ignorance and delusion we perceive self in what is not self. When we are caught up in this delusion, we view, perceive and think erroneously. These wrong views prevail in the world until a very few amongst us accept only the original suttas – the scriptures – and be true to it – be committed to it. The Supremely Enlightened One reveals the true nature ONLY if we commit to the Truth. The Blessed One proclaimed how one can achieve deliverance from ignorance and delusion, but hardly anyone amongst us will ever get there.

Supreme Buddha explained this WHY with a simile. The Blessed One placed a little soil on the tip of a fingernail, and compared that to all the soil on this great Earth. The soil on the tip of the fingernail is insignificant in comparison to the soil on this great Earth. Even so insignificant, are the beings who reach perfect sanctity, the final liberation from suffering. Here Buddha is referring to Sotapanna Disciples.

A Sotāpanna (Pali) or "He who entered(āpanna) the stream(sota)." ‘stream” is a metaphor for the third of the Four Noble Truths, Noble Eightfold Path. A stream which rigidly flows will not stop until it enters the sea. A Sotapanna has completely entered in to the Eightfold Noble Dhamma Path (has gained the first magga-phala). So he will surely achieve Arhathood within seven births that are born in human and heavenly happy realms and his spiritual development will not descend.

Therefore, it is clear that this is not something that can be accomplished effortlessly. Each individual has to put forth the necessary effort, and work out his own deliverance with mindfulness. A noble disciple, who possesses unflinching energy with firm determination to realize the Four Noble Truths, will be able to work out his deliverance.

Let’s Live Close to the Perfect One, the Tathagata.

I have not known all that many practitioners of The Mahasi method, but I know it is very popular. The criteria for sotopanna are self-evaluated. The only criteria which the Buddha always includes in his definition is "unwavering confidence (or faith)". Sometimes he also includes the Five Precepts, sometimes he also includes the other three parts of Right Speech, and sometimes in addition includes contemplating the chain of causation. So if people state that they have achieved unwavering confidence in the Triple Gem, who could say otherwise? The only check on this would be to ask the same person many years later if they still believe they have unwavering confidence.