hitting on arms during rebound

[Adam]

Kelvin,
No one is saying it's a foul to violate the air space above another player. Only that contact in someone's air space is the responsibility of the player who does not own that particular air space.
If A1 is shooting a jump shot and his arms are in B2's air space, any contact would be the responsibility of A1, and B2 cannot be penalized for it. Per rule.
The rule was not written to allow B2 to wave his arms sans contact. That's already allowed. It was written to allow B2 to make contact in his own air space without penalty.
There is no provision that states his arms must already be there. Therefore, it looks to me that he may actually initiate the contact as long the contact is made in his own air space.