[wwcfoa43]

Perhaps you can think of it as a retroactive dead ball foul. The foul occured before the snap but you did not know it until after the snap. So you kill the play and enforce as if the play never happened.

We have similiar "retroactive" instances in the Canadian game. Pass Inteference occurs when the ball is in the air while illegal contact occurs on passing plays before the ball is in the air.

If the offense commits illegal contact then we only know that it is a passing play once they throw the ball. So we flag the IC when the ball is in the air even though the foul by definition occured before the ball was in the air.