yeah - i noticed the same thing - it took longer to kill/eat the tiny pinky, which was almost too small for the snake to squeeze. This is why I immediately went back out to the store to purchase larger mice (So, in total, she ate two pinkies and two regular). The person I adopted the snake from was a dunce, to the point where I look like a pro in comparison.
I still stick to my initial statement that if a BP is hungry enough, it will eat anything small that moves. Maybe captive bred BPs would allow themselves to starve to death if no mice are available, but the primary goal of any creature in nature is to live, mice or no mice. BPs included.