[JRutledge]

I think you are making this more complicated than it needs to be.

A player is not out of bounds until they either touch out of bounds or ruled out of bound by rule. In this case the runner is nothing until they touch something out of bounds. If forward progress is at issue and they are airborne, then they are considered to be where they crossed the intersection once they have been ruled out of bounds. That is not the case in the play you described. So if they leap and touch the pylon or foot touches, they are for the purposes of this discussion still in-bounds. As it relates to the end zone the ball must cross on the in-bounds side for an airborne player to be awarded a TD. If they are touching the ground, they simply have to reach past the goal line (in-bounds or out of bounds). That is why you hear "Goal line extended" being used because it applies not matter where you are in the field for a player touching in-bounds.

Peace