koug, it is a valid question. I think they just enjoy messing with you.
My guess would be that 1st, it takes away the roll. If the screener is getting bodied, then he's not going to get off for a clear path to the basket. 2nd, you can still get the ballhandler to change his path enough to not come off clean for a shot. 3rd, bigs are used to bodying up on defense so they're more apt to get away with a little more contact on the screens. 4th, it fits his ball pressure style, hedging and coming under screens allows for more gaps and space for shooters. 5th, in his mind, help should be there if the bump and isn't clean and the defender comes off trailing.
Huggs also teaches pressuring the ball and taking away the middle of the floor to the point of giving up baseline at times, which to many basketball folk is a sin. The movement of your defense can set you up for charges or forcing quick shots or bad passes off of it, but you've got to be trained well to rotate and help. Bob Knight uses this technique with his man D as well FWIW.