I think the answer to your question is "no". The tour descriptions do not mention side trips in the van and none of the journals I've read of van-supported tours mention them either.
If you're staying with the group, I agree with John. I'll note, though, that membership in the group that was close to us was somewhat fluid; people would take off on a side trip for a few days to do their own thing, and then might rejoin later. A few left the trip, and some of the journals I've read suggest other people might hook up with the group later in the trip.