Thrower Commits Foul

[Adam]

Sounds like an intentional foul to me, but not because thrower reached through the plane.

Change it for a moment: A1 is standing on the court with the ball, guarded by B1. He gets tired of the pressure, puts the ball in his left hand as he turns his body. He then puts his hand on B1's chest and shoves him backwards. The arm bar, the push off from a dribbler, the push off in the paint, these are all considered normal offensive fouls; but none involve an offensive player who essentially stops playing basketball for a moment to shove a defender.

You were right, by rule; it's a judgment call.