score:3
The statement that the cited website is the official website for Antelope Canyon tours is false. I found a list of companies which offer tours to Antelope Canyon (note that the prices listed in the table are not accurate as of today). It looks like one can almost always find availability for any date since there are more than 10 companies organizing tours.
Upvote:2
There are multiple Antelope Canyons you can visit. Examples are:
Here is the list from the Navajo Nation Parks & Recreation (They oversee all Navajo Tribal Parks on the Navajo Nation Reservation): https://navajonationparks.org/guided-tour-operators/antelope-canyon-tour-operators/
During the summer the more popular are very crowded. (There are some nice videos on YouTube showing how uncomfortable it is for the visitors).
I personally went on the "photo tour" in the Antelope Canyon X. As it is less popular we had enough time to take a lot of good photos. We also intended to go to the Upper Antilope Canyon, but the staff was so rude, that we decided we did not want to spend time with these people.