BYU isn't looking to outmuscle you off the line of scrimmage. They are looking to force you into an unforced error by making big guys with gap control responsibilities move. This is why Algeier is so effective because he can quickly cut back into the open hole where a defensive player has lost gap control either by lack of discipline or physical ability.

When defenses do maintain their gaps you see BYU backs run to the edge and then try and fall forward or out of bounds for whatever positive yards they can get. The key is getting whatever positive yards they can get to make the later down and distance easier to handle.