LGP on Airborne Shooter

[Jurassic Referee]

This is a play situation posted on the NFHS forum.....

Play: A1 with the ball leaves his feet to attempt a shot. Defender B1, who had a legal guarding position on A1 before A1 left his feet, now moves laterally(sideways) into the path of airborne A1 after A1 became airborne. Note that B1 does NOT move forward towards airborne A1, just laterally. If contact occurs, who should the foul be called on?

I posted this play because a nameless poster over there(Mark T. DeNucci Sr.) insists that a defender can legally move laterally into the path of an airborne shooter AFTER the shooter became airborne and still maintain a legal guarding position. Iow, if the defender does move laterally into the path of an airborne shooter after the shooter became airborne, it's a player control foul if contact occurs.

Note that the following case play was also cited:
10.6.1 SITUATION C: B1 is standing behind the plane of the backboard before A1 jumps for a lay-up shot. The forward momentum causes airborne shooter A1 to charge into B1.
RULING: B1 is entitled to the position obtained legally before A1 left the floor. If the ball goes through the basket before or after the contact occurs, the player control foul cancels the score. However, if B1 moves into the path of A1 after A1 has left the floor, the foul is on B1. B1's foul on the airborne shooter is a foul during the act of shooting. If the shot is successful, one free throw is awarded and if it is unsuccessful, two free throws result. (4-19-1, 6-6-7-4, 10 PENALTY2 5a)

Again, can a defender who has established a LGP before a shooter became airborne now legally move laterally into the path of that shooter after the shooter became airborne?

Thoughts?