Is the Watchtower afraid of what maybe being discussed among JWs at this meeting?
I've heard that some Elders who conduct the meetings have been asked awkward questions about WT teachings.
It is too bad in a way because I always enjoyed the book study. There was always a little more open discussion during that meeting since it was a smaller group.

From personal experience, there has been, at times, the discussion of issues that the WT would rather we not speak of during the book study. I remember as a kid, the whole 607B.C.E. issues was raised.

I also found many (but not all) of the elders who conducted the book study, were not only friendlier, but much more willing to discuss the issues brought up in the study in a personal way. For instance, the last book study group I was with, the elder gave some of his experiences from when he was a Catholic.

The WT has already (in the September Our Kingdom Ministry) expressed their irritation over groups meeting independently to discuss the Bible. I'm sure this will be explained the same way, that having the book study at the Hall will insure that everyone is getting their "food at the proper time.":

You know, if I was an elder, I'd be a little pissed over this. There's really an air of "we don't trust you elders on a person-to-person basis."