The N.C.A.A.— “an open field block against an opponent that is initiated from outside the opponent's field of vision, or otherwise in such a manner that the opponent cannot reasonably defend himself against the block”

Was watching Northwestern victory today and the QB scrambled out of the pocket with a rusher in pursuit and a lineman pealed back and bumped the rusher away from the ability to tackle the QB. It was ruled a blindside block and clearly the rusher didn't have a chance to defend himself even though it wasn't a very hard hit.

My question is, why is this a penalty? A receiver catching a ball or a running back is often hit with tremendous force without seeing the tackler. It is still considered a sack when the left tackle missed the block and the up-field looking QB gets decapitated by the defensive end. So why is it not merely FOOTBALL when a player takes a good clean shot when in the action of a play?

Or does it simply mean offensive players are studs and must take the shots while defensive players needing blindside protection are not studs?

There used to be a video of Tyler Futrell delivering a devastating block on an EMU linebacker to spring Tyler Tettleton for a big run.

Would that block now be illegal?