Running TD vs Passing reception TD

[Usbcbowler]

I have somewhat of an idea of what answer will be but I would like someone who knows the rules to explain them to me

Ball Carrier TD
I am under the impression that when the ball crosses the goal line it's a TD. If ball carrier has possession at the time ball crossed goal line

Now let's say ball carrier dives over pile with ball extended while he is diving and ball is knocked out of his hands before he hits ground or lands on top of players. I think they still call this a TD even though player did not control ball through end of play

Receiving TD
Now let's say a receiver goes up for a pass, lands with both feet in bounds and has possession of ball with no movement in his hands and is knocked to the ground a second after coming down with ball and as he is coming down and hits ground ball moves in his hands and touches ground. I think this would be called an incomplete pass

Question is why as soon as ball crosses GL on running play, regardless of play being completed, it's a TD and as soon as ball crosses GL on passing play its not a TD until completion of play

Thanx for anticipated answers

 

[GeoRingoes]

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[Usbcbowler]

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[SirPerceval]

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