It's possible he didn't feel the need to constrict because of the drop feeding, as others mentioned (which is totally fine if he'll eat that way), but it also could be because those look like very undersized meals for him. BP's generally come out of the egg eating hoppers and move up quickly to small adult mice. :) It's good that you fed two fuzzies, but hopefully he'll get bumped up to something sized more appropriately soon.