If you can review an out of bounds call at the end of the game, surely you should be able to review this. It was clearly not over and back but I understand how they could think it was based on the angle of the pass. That said, they guessed, which should not happen.
As someone stated, generally, you have to have both feet and the ball in the front court to have frontcourt status. One exception, if you are straddling the division line holding the ball and pick up the foot in the backcourt, you can't put it back down without violating. If the backcourt foot is the pivot, you can pivot the front foot back and forth without violating.