This opinion will not work for NFL football. If what you say is true, then the technique I would be teaching all pass defenders is if the WR turns back towards you don't play the ball just run straight into the WR. It won't be pass interference.
You have spent time giving your opinion, but I dare you or any other who claim the defender turns his head back to show it in a video or picture. From even the grainy pics I isolated he never looks back at the ball. He just runs right into Brown. If you look at this feet he doesn't even stops striding. He just crashes right into him.