Are JWs restricted from expressing things in their own words?

I do not have access to the materials that the elders use to train people in public ministry, but I suspect that you've encountered Jehovah's Witnesses that were uncomfortable speaking in their own words. The Watchtower website indicates that Jehovah's Witnesses are allowed to express things in their own words:

SHARING BIBLE TRUTH WITH OTHERS

As faith grows in your heart, you will find it hard to keep what you have learned to yourself. (Jeremiah 20:9) You will be strongly motivated to speak to others about God and his purposes.—2 Corinthians 4:13.

You might begin to share Bible truth with others by tactfully speaking about it to your relatives, friends, neighbors, and workmates. In time, you will want to share in the organized preaching work of Jehovah’s Witnesses. At that point, feel free to talk things over with the Witness who is teaching you the Bible. If it appears that you qualify for the public ministry, arrangements will be made for you and your teacher to meet with two of the congregation elders.

This will enable you to get better acquainted with some Christian elders, who shepherd the flock of God. (Acts 20:28; 1 Peter 5:2, 3) If these elders see that you understand and believe basic Bible teachings, are living in harmony with God’s principles, and truly want to be one of Jehovah’s Witnesses, they will let you know that you qualify to share in the public ministry as an unbaptized publisher of the good news.

On the other hand, you may need to make some changes in your life-style and habits in order to qualify for the public ministry. This may include stopping some practices that have been kept secret from others. Hence, before you ask about becoming an unbaptized publisher, you need to be free of serious sins, such as sexual immorality, drunkenness, and drug abuse.—1 Corinthians 6:9, 10; Galatians 5:19-21.

While the Bible is a reference used in our worship it is far from our most prominently used publication. Of the approximately four hours per week of group worship engage in at our local places of worship (Kingdom Halls), routinely the Bible, by itself, is only discussed for 10 min. The remaining 230 min. of weekly instruction is culled entirely from Jehovah’s Witnesses publications with their own unique concepts and phraseology. Peppered throughout these publications are many scriptural citations but the bulk of the text is from writers originating at the world headquarters in New York.

In fact Jehovah’s Witness publications refer to this unique way of speaking as ‘the pure language’ stating principally that “The pure language is the truth about Jehovah God and his purposes as found in his Word, the Bible.” (Watchtower August 15, 2008) Secondarily, the article goes on to parallel learning an actual spoken language and this ‘language of concepts’ saying, “Imitate fluent speakers. Students of a new language are encouraged not only to listen carefully but also to try to imitate, or mimic, the pronunciation and speech patterns of fluent speakers. This helps the students to avoid developing a heavy accent that may later hinder their efforts to communicate. In a comparable way, we should learn from those who have mastered the “art of teaching” the new language.” (Reference: http://wol.jw.org/en/wol/d/r1/lp-e/2008604)

This ‘imitation’ is I believe what the original questioner was getting at. Those who are the main speakers in the congregation and at our larger conventions use phraseology that is unique to the religion and those who aspire to someday be in their position imitate this speech. The lay members of the congregation adopt the speech because this is what they are hearing from those speaking and what they are reading in the Jehovah’s Witnesses’ publications. Phrases such as ‘field service,’ ‘theocracy,’ ‘remnant,’ ‘governing body’ are products of our religious beliefs but certainly not concepts or terms Jesus Christ used.

Another Jehovah’s Witnesses publication entitled Theocratic Ministry School Guidebook acknowledges this quite clearly, stating on page 112: “Our study of the Scriptures and the Watch Tower Society’s publications has given us a vocabulary of terms quite strange to those unacquainted with our work. If we were to explain the truths of the Bible to some audiences, using such terms as these, either much of what we say would be lost or our speech would be entirely unintelligible.” (Reference: https://wol.jw.org/en/wol/d/r1/lp-e/1101971070#h=20)

In response to @4castles comment: It is disingenous to overstate the impact the Bible has on the Jehovah’s Witnesses vernacular versus the impact of Jehovah’s Witnesses publications. As mentioned earlier in this post, yes, the publications are peppered with scriptures, however they are re-framed in the JW vernacular.

In other words JW publications often cite a scripture, then translate the ideas of that scripture into vocabulary that Jehovah’s Witness have become accustom to. Again, with the exception of approximately 4 minutes of Bible reading all of the scriptural discussion for both meetings are facilitated via workbooks, outlines, prepared videos and publications. Generally the content of the workbook and outlines are expected to be adhered to closely.

This is the case for those presenting at Jehovah’s Witnesses annual conventions as well. The material originates from world headquarters and is heavily scripted. From experience, these outlines (scripts) are expected to be adhered to closely. I think it’s safe to say that we make the statements: “The Society (meaning the group of individuals responsible for writing the various publications) says” or “The Watchtower (the magazine) says” or “The publications (books writen by the JW oranization) say” just as often as we state “The Bible says.”

Specific portions of our services are set aside for demonstrating and practicing what we will say when preaching in the local neighborhoods. While encouraged to make these discussion our own, chatting extemporaneously with a stranger is not easy for most. Naturally most JWs fall back on a rehearsed sermon — that is exactly what the OP is hearing when talking to JWs.

Q. Are JWs restricted from expressing things in their own words?

A. No.

We who are members of the worldwide unified Christian congregation of Jehovah's Witnesses both can and do express ourselves / our Bible based beliefs in our own words, however, we would much rather and prefer to express ourselves / our Bible based beliefs in the way in which our Leader, King and Exemplar (Jesus Christ, the only begotten Son of Jehovah God) expressed himself / his Bible based beliefs... and I quote King Christ:

"Jesus, in turn, answered them and said: “What I teach is not mine, but belongs to him that sent me. 17 If anyone desires to do His will, he will know concerning the teaching whether it is from God or I speak of my own originality. 18 He that speaks of his own originality is seeking his own glory; but he that seeks the glory of him that sent him, this one is true, and there is no unrighteousness in him. " ~ John 7:16-17

"because I have not spoken out of my own impulse, but the Father himself who sent me has given me a commandment as to what to tell and what to speak. 50 Also, I know that his commandment means everlasting life. Therefore the things I speak, just as the Father has told me [them], so I speak [them].”" ~ John 12:49, 50

Again, Christ is our PERFECT example whom we strive to the very best of our imperfect ability to imitate (1 Peter 2:21). Was Jesus Christ restricted from expressing things in his own words? We pattern our way of life and the way we teach on him.

~ NOTE: I am a dedicated and baptized member of the worldwide unified Christian Congregation of Jehovah's Witnesses.