interesting boo-boo

[Lotto]

I'm on the side of blowing the whistle as soon as the dribbler steps out of bounds and not waiting until the ball rises to his/her hand again. Here's an analogous situation that explains why I believe that.

Suppose that dribbler A1 charges into B1 "in between" dribbles, so the ball is not touching A1's hands. You're not going to wait to see if the ball comes back up and touches A1's hand before whistling a player control foul, right? That's because the dribble hasn't ended. Similarly, in the present scenario, A1 is still dribbling while the ball is not touching his/her hand, so stepping on the sideline is an immediate violation.