I think there is some truth to that...but it isn't black and white.
You don't win the MAC East title, and beat Northwestern, with 85 guys that are sloughing off.
But you probably don't go from a 2.4 to a 2.9 overall team GPA in one semester without some players being held accountable for their classwork, who weren't in the past.
I think all you need to know regarding the buy-in of the incumbent players to the new staff is seen in the lack of transfers.