I like Fatso's take. Once the player's progress was wrapped up, this play should be shut down for safety purposes and not allow the defense to take a free shot at the QB. Nothing good is going to happen afterwards (and did not).
That coach thought he was going to be clever by keeping the ball in bounds too. So, if we don't shut this play down, then we are going to possibly have two fouls to enforce. The down will be repeated with basically 5 yards back from the previous spot and then we go forward 15 for the UNS, correct?