I also believe the snake's aggression is unrelated to the amount of food. Usually after my snakes eat, they will hide and not move much for a day or two until they have digested. After that they may come out and move around a bit, and then they usually defacate. What your customer was seeing was probably "digesting periods" several times in a row due to the frequent feeding.

Tell him to get some good leather gloves and learn to handle the snake, instead of just stuffing him with mice!