It is not! Wilderness is small like a 10g tank!
But seriously, the larger the tank, the more difficult it is for you to keep the husbandry requirements met and the more money you have to dump into it to get it to where you need it. A BP doesn't need that much room because they aren't very active snakes and don't move around a whole lot, usually the only time I catch mine out of her hide is when she is hungry. But really, I don't think that the extra space will stress the snake out at all if you have it decorated properly with fake plans, rocks, hides, waterbowls and the like.
When she gets bigger I'll move her to a 30g, but thats for my pleasure only, not for hers, I'm sure she won't really make use of the extra space. I just enjoy the decorating and bringing a little bit of the wild into my home. I would never do anything over 30g for a BP because the husbandry requirements will get more difficult to meet, the cages keep getting more expensive, it requires more bedding, more decorating and quite a bit more money.