I've been trying to reconcile these two case plays all night. Here is my latest version.
5.2.1C
A ball that is thrown into a teams own goal from behind the three-point arc scores three points. So a ball that is thrown by A1 into A1's goal from behind the three point-arc scores three points regardless of being legally touched by a B player inside or outside A's three-point arc. It is the result of an action started by A1 and ending by going through A's basket.
4.41.4B
Since the try has ended and team control does not exist, any touch by B1 would now be considered a tap, try, throw or action started by B1. By rule, a three-point goal can only be scored at a teams own goal. So B1 can't score a three-point goal at A's basket. As opposed to 5.2.1C where the action is clearly a thrown ball (still in TC) by A1.
5.2.1D
This case play has a throw-in by team A being touched at the FT line and then goes directly through A's basket. Again no team control so any touch by B, whether inside or outside A's three-point arc would result in two points. The throw in ends and B cannot score a three-point goal in A's basket. My thoughts are that if A1 deflected the throw-in and was outside the three-point arc, it would score three points for A.
I am having a hard time putting my thoughts into words on this one. I hope I have described it coherently.
And I can't place trajectory as having anything to do with it.