I think a little bit of it is that he's getting called for fouls because he's trying not to foul. Refs favor the aggressive player. Dustin hasn't become an aggressive defensive player yet.
He may also now be fighting a reputation. Basketball in general but maybe the PAC worse than some other conferences, refs tend to call a lot of stuff on reputation. Earlier on he was doing a lot of fouling instead of moving his feet, now he is moving and in better position but they are still calling him based on what he did before.