Sooooooo......what timing criteria are we supposed to use to determine what interval is needed to make the shot a 3 or a 2? Iow, what is a "split second"? And why is it only a "split second" and not longer? If there's a 0.3 seconds difference between the foot on the line coming up and the foot behind the line coming up, does that make it a 2? If there's a one-second interval between the feet coming up, is it a 3 now? If the player stands on the one foot behind the arc like a stork for 10 seconds or so, and then goes up, is that a 2 or a 3?

Just wondering how you want us to call this play......

You are the one speaking in absolutes, not me.

I clearly stated an every game scenario:

A1 is attempting a try.

A1 begins his/her shot with their right foot touching the 3 pt line and their left foot completely behind it.

During this jumper A1's right foot leaves the floor slightly ahead of their left foot...slightly means before, where it is barely perceivable and not blatantly obvious, IOW no Karate Kid stork stance.

Are you ruling that a 2 or a 3?

As already stated before, I'm ruling it a 3. Once A1 is standing on his left foot behind the arc with his right foot in the air, A1 is considered to be behind the arc-as per rule 4-35-1(c). If A1 now shoots, that's a 3. The time frame following A1 lifting his right foot is meaningless. It doesn't matter if it's a nanosecond or 34 minutes. Once the right foot is lifted, A1's location is behind the arc because the only part of his body touching the court is behind the arc.

If you, as a ref, can determine the foot on the arc came up before the foot behind the arc, then I think you have to count it a 3. If you can determine that, then it was obvious. If you cannot determine that, then you leave it as a 2.