I stand corrected. Props to Jefferson: For an over-and-back violation, the ball itself must gain frontcourt status first.
The ball is considered in the frontcourt when:
The ball and the player controlling it both have frontcourt status.
For a dribbler, the ball gets frontcourt status when both feet and the ball have crossed the division line.
If a player is dribbling and:
Crosses midcourt with his body,
But the ball never actually gains frontcourt status (for example, the dribble remains bouncing on or in the backcourt),
Then steps back into the backcourt,
there is no over-and-back violation because the ball never established frontcourt status.
What the heck was Alvarado doing?
He catches the ball, stands there for what felt like two full seconds while the clock is running, then appears to dribble back into the backcourt and gets bailed out by a foul call.
Just an absolutely awful possession.