Yeah, you take the holes 4+ inches deep, but you are taking so much out of the weight block it changes the dynamics of the core..
He said that he will sell you a 16 lb ball for 95 bucks and drill it out 4+ inch deep holes or he will drill you the same ball for 130 at a 15 lb.. it's because not many people throw 16 anymore and it is a way to get rid of your 15 lb stock or to get that sale at 130...