I recently listened to Brother Dunlap's audio recording http://www.jwinfoline.com/Page/audio.htm
It makes much more sense now.. Anytime a witness sits down to prepare a part, or to write an article, his primary objective is to write the article in agreement with "Current Light". With this objective, naturally he will primarily consult the Insight book and the Watchtower Library, the Bible would be used only as a source for Supporting Quotes. It would not be necessary to fabricate new interpretations, they have already been done.
This leads me to question, the person(s) that establish "New Light" what might their motives be? Is it more of the same? They are working with he set of doctrines, they have inherited?
It's amazing that the only "Biblical Commentary" type book the Organization has ever produced (Aid Book) resulted in 2 or 3? of the 5 writers either leaving or getting booted from the Org.