All, please note the language of 4-2-4 is nearly identical today as it was in 2011; the only difference is the AR references.
And please note that all play situations listed under the "Airborne Ball Carrier" section of 2011 CFO Bulletin Intentional Grounding/Airborne Ball Carrier:Extending the Goal-Line Plane have been, and are still, ARs (see AR 8-2-1-V thru VIII), since 2011.
Also note that another bulletin that same year (2011), Forward Progress for Ball Carrier Out of Bounds, interpreted that a ball carrier striding across the sideline is also airborne; thus, the goal line is not extended beyond the pylon for him. If he can make the ball (in possession) pass inside or over the pylon before he touches the ground OB, touchdown (because the ball broke the plane of the goal line before it crossed the sideline) (AR 8-2-1-V). If the ball is outside the pylon as he strides across the sideline and then he touches the ground OB, not a touchdown - he doesn't get the goal line extended outside the pylon (and the ball crossed the sideline without breaking the plane of the goal line).
It boils down to this: If neither the BC nor the ball touch the pylon or ground in the end zone (before any part of the BC or ball touch something OB other than the pylon), the BC doesn't get the goal line extended (outside the pylon). But, he does get the pylon, including the goal line (extended) directly above the pylon. So, if he can manage to get the ball over the pylon while running or diving out of bounds, that's a TD.
Robert