Y'all may be misunderstanding the rule a bit. The word "directly" refers to "...the plane directly above the frame of the body of an opponent." Rather like the plane of the goal line is directly above the goal line, so is the plane of the frame of the player's body. This is as distinguished from being slightly in front of the opponent, or angular from the body. This rule change for 2018 was one of the best changes we've seen in many, many years. Rather than any leaping - even straight up - being a foul, the leaper has to get into the plane that is directly above the opponent. Since the frame of the body is at the "...shoulders or below...", on this play, it is pretty clear that the receiving team player got into the plane of both the snapper and the guard. I can see passing on the action with the guard, since he didn't touch the guard. But he lands on the snapper's left shoulder and contacts the side of the snapper's head as he is trying go over. Contact is not required for there to be a leaping foul. It is an indicator, but it is not required. (That's why I say I can see passing on the action with the guard, since he doesn't make contact with the guard, and he is moving away from the guard's initial position when he began his leap. He probably, technically, enters the guard's plane, but it is negligible enough to discount.)
A 'gap' would be the clear space between two players (exclusive of arms outside the frame of the body). If that clear space is less than the width of the leaping player's body, it is going to be difficult for the leaper to not get into the plane of one or both of the opponents on either side of this 'gap.' If he stays on the ground, he is permitted to try to charge through a 'gap' that is less than the width his body. But, if he tries to leap over a gap that is less than his body width, he is almost sure to get into the plane of one or both opponents.
As in this case.
Robert