That is flat out ridiculous, there is no possibility of calling a timeout DURING A PLAY. When the ball is snapped, no timeouts can be called.
Otherwise, coaches could call timeouts right before a player crosses the goal line.
There is virtually no way to define prohibiting timeouts right before a snap. The best I can think of is that coaches must be allowed to call a timeout at the instant they want it, not phrase it as, "I want a timeout right before the ball is snapped" Then the official waits until the ball is snapped, and halts the play.
This way, the coach must decide about when the ball is being snapped, then call the timeout right then. If he can't get the words out before the ball is snapped, the game is over. None of this "I want a timeout right before the ball is snapped!"