I will give you one example of what is wrong with others who make that statement.
Supposing the WTS INC/GB decided that the trinity is now going to be a teaching. How many JWs would object? Did they ALL know that when they got baptised that they have to accept as truth and "adjust their thinking" so as to agree with EVERY TEACHING IN ANY GIVEN YEAR that the GB teaches or else have this scripture applied to THEM?
2 John1010 If anyone comes to YOU and does not bring this teaching, never receive him into YOUR homes or say a greeting to him.
The answer is NO.
But the FACT is that any JW would HAVE to accept ANY teaching from the GB.
When a JW gets baptized, they don't realize that they may have gotten baptized because they believed AT THE TIME, that the teachings of the GB were "the truth". Along with that, they belived that truth does not change.
JWs DO NOT KNOW that they HAVE to believe every teaching form the GB is the truth NO MATTER WHAT THE TEACHING IS AT ANY GIVEN TIME, when they get baptized.
And the WTS INC, should make that CRYSTAL CLEAR to it's potential adherents/followers BEFORE THEY GET BAPTIZED IN ASSOCATION WITH IT"S ORGANIZATION.
Of course, they wouldn't do such a thing. Because then the organization would have NO CONTROL over it members.
And members = $$$$$$$$$$$