Let's also remember there is no reason why a human should be calling balls and strikes in the first place. One can't get bent out of shape when they make an error, and also want them to call balls and strikes.
I think in this case, the ump got blocked out by the catcher while the ball was traveling, and when he made his decision, the ball was in the zone, but that was before it crossed the plate. There was some anticipation in the call.