The entire point is that they aren't protecting themselves, but the act of sliding gives them the protection. If CV would have been nailed by a defender from the point that they ruled him down to before he was physically down we'd be losing our minds if they hadn't called a penalty.
The rule is fine, it needs to be called consistently and needs to be challenged by the god damn coach if it's a game-deciding call.
Its an impossible thing to call. Somehow, the ref got it exactly right but that was luck. The FSU ref missed it by 2 yards. Determining where a butt is lowered in real time is impossible. Should be where the player's knee hit like every other play and like it was for 100 years. The NCAA lost their mind over the fake slide and they over-corrected and effed everything up.