There are old vehicle designs were the grill causes the pedestrian to rotate 90° into the windshield. Your assertion of how collisions work is predicated on changes to hood and front design that already account for pedestrian collision physics. But you’re implying this has always been the case and it has not.

This is, for instance, a big part of why the Mini Cooper is no longer mini. They had to lift the hood profile to reduce angular momentum.

Also why the forward raked grill designs of the seventies are gone never to return. Those suck pedestrians under the car, which is almost always fatal.