I watched that youtube link you provided. I didn't realize this one rule: if a player is touching inbounds in either the endzone or in the field of play, and the ball crosses the goal line extended then it's a TD. So - let's say a player catches a pass and is dragging his foot inbounds at the 2 yard line and he sticks the ball past the goal line extended it's a TD? (even if the ball is outside the pylon at all times).
Based on your description both boxes are checked.
The goal line extended goes off into infinity if, and only if, the runner is touching inbounds
(2-26-3)If, while touching inbounds, the runner holds the ball over the Goal Line extended
(2.26-3 SITUATION)The result of the play as your described it, is a Touchdown.