Ya know, I think that comment may be a little off base. I don't believe you'd get the same ambience with a tour as you will while sitting there enjoying the food. For us, at least, it's not about the cost of the food. At home we often go to restaurants just for dessert. It has never been an issue. Why should it be any different at DL?
I've been to the BB exactly once (my previous DL companion was a cheapskate, stick in the mud). During our last trip, the girls and I went for dessert only. We did have a table at the back, but that wasn't an issue. Our server was more than pleasant. Our service and food were both great. We were in and out within 30 minutes. I had made PS and waited just like everyone else. I also told them when I made the call that we would only be there for dessert as neither of the girls could find anything on their menu they thought they'd eat. They're both incredibly picky.

We even ordered 3 desserts and shared. I also left her a tip that was bigger than normal for her wonderful service.
Maybe we're an exception to your rule, but we had a lovely experience.
I see no reason not to go just for dessert if that's what your budget (both time and monetary) allows.