A game-winning score via run as time expires has to be one of the rarest plays in the NFL, no?

That’s just R bein’ R.

How is it not true? I’m aware of the rule - it specifically goes on to define “defenseless” as a player on the ground. As opposed to Rule 9-1-3, which pertains to using the crown and omits the “defenseless” requirement.

For whatever it’s worth, by rule, a sliding player is not defenseless until he is on the ground. For there to be targeting, has to be with the crown of the helmet.