I think BP's tend to cruise around a bit more than most people think. My BP's in larger tanks are all very active at night (and they are not stressed), they also tend to be more active when held in general. They seem to enjoy being held more than the tub snakes too.

And some of my rack housed BP's are more active than others. I have a big girl who just lays on the cool side all the time, and a male who hangs out on the warm side most of the time, in the same rack. Every snake is different.