Calhoun's hedge strategy was "step and recover", to give the guard just enough time to fight over the screen. We tended to give up some open 3s when the big dropped too quickly or the guard didn't get through the screen.
Last night, we fouled more in the second half, when we mostly abandoned the hard hedge, so your point on it being the cause of fouls is still off. Our bigs, for the most part, have not fouled away from the basket much this year, and we're fouling around the basket no matter what strategy we employ.
My point is that there is more than one way to skin the proverbial cat. Florida won two straight championships blitzing ball screens with a hard hedge and mixed it in last year as well. Baylor won a championship the same way. Houston does it regularly. The Roy Williams Carolina teams mixed their ball screen defense up a ton. Other teams switch everything (Duke, Villanova under Jay Wright).