Backcourt violation? 2007-08 Interp

[rfp]

Reviewing old interps and am struggling with this one.

SITUATION 7: Team A is making a throw-in near the division line in the team's backcourt (Team B's frontcourt). A1's throw-in is deflected by B1, who is applying direct pressure on A1. B2 jumps from his/her frontcourt, catches the ball in the air and lands in the backcourt. RULING: Backcourt violation on Team B. The throw-in ends with B1's deflection (legal touch). When B2 gains possession/ control in the air, he/she has frontcourt status. A backcourt violation has occurred when B2 lands in backcourt. (9-9-1; 9-9-3)

Since Team A is making the throw-in, why doesn't 9-9-3 apply where the "while on defense" exception covers a defensive player going from his frontcourt to his backcourt? The tip ends the throw-in, but a defensive player can still go from his frontcourt to backcourt while making a steal, no? Just because the throw-in was tipped doesn't mean B2 is no longer a defensive player.