Situation: Where to inbounds the ball

[Lotto]

The situation is different under NCAA rules. Rule 9-5.1, which defines the throw-in violation, says that a thrower-in shall not

b. Fail to pass the ball directly into the playing court so that after it
crosses the boundary line, it touches or is touched by another player
(inbounds or out of bounds) on the playing court before going out of
bounds.

Rule 9-5.2b says that no player other than the thrower-in shall:

b. Be out of bounds when he or she touches or is touched by the ball
after it has crossed the vertical inside plane of the boundary line.
Repeated infractions shall result in an indirect technical foul.

So the violation described would be, under NCAA rules, a violation on B2 and not on B1. As such, the ensuing throw-in by A would be on the sideline near B's bench.