Alternating Possession Arrow Change

[BktBallRef]

Wow, this sure has been complicated for no reason.

6-3-4
The direction of the possession arrow is reversed immediately after an alternating-possession throw-in ends. An alternating-possession throw-in ends when the throw-in ends or when the throw-in team violates.

4-41-5
The throw-in ends when the passed ball touches, or is touched by, an inbounds player other than the thrower.

Notice that 4-41-5 does not say "...when the passed ball LEGALLY touches..." The arrow is switched in cases when the kick occurs.

The running the endline situation is a completely separate issue that's addressed by a specific rule and case plays.

As BZ said, apples to oranges.