about crossing the plane (albeit no video review back then).
A player is not out-of-bounds on the sideline until some part of his body actually touches the ground out-of-bounds. If some part of the body crosses the plane in the air out-of-bounds, the player is still not out until some part hits the ground.
But a player scores a touchdown if he just crosses the plane of the end-zone with the ball while the ball is still in his possession. The pylon indicates the corner of the end zone, i.e. if a player has possession of the ball and hits the pylon with the ball while still in bounds, it is a touchdown. So the air space directly above the pylon also represents a touchdown.
The ball clearly crosses the area above the pylon while the Pitt runner is still in bounds.