The finalizing of the bible canon as we have it is something that JW indoctrination builds a fence around to protect you from the logic of your own thoughts and questions.
Think about it. What are two of the biggest doctrines that JW's rail against? The imortality of the soul and the trinity. HOW DID THESE IDEAS GET INTO "CHRISTENDOM"? Through the votes that included the Athanasiun creed, the Council of Nicea, and other such "apostate" councils. These were also the people (and their theological descendants) who compiled the traditional bible canon.
If you believe JW's, you believe that somehow Jehovah was powerful enough to make sure that the correct 66 books were included in the bible canon, but not powerful enough to stop man from incorrectly identifying god as a trinity. He was not powerful enought to clearly teach the idea of whether the soul is seperate or the actual person.
These are questions I actually asked myself while I was in the borg, but the JW theology got in the way, and I barely dug at those questions. (this is also why I believe that cognitive dissonance exists). I held two totally contradictory ideas in my head. That apostates were used by Jehovah to assemble the bible, and that these same apostates poisoned the book Jehovah used them to assemble.
It certainly isn't a question that JW's in particular can answer satisfactorily. The GB compares those who inserted the trinity for example as agents of Satan. So how does Jehovah use these agents of Satan to compile the bible canon?