The argument had to do with arm strength, not the release time. So it's based on the time and distance from the release to the time it reaches the receiver. Two throws, Mac's is 20yds, Zappe's is 21 (both air yards). Mac threw his flat-footed, Zappe had to crow-hop and gun it. It was basically for all the people that said Mac had a weaker arm. It just isn't the case, at least right now.
Again, as I said in another post, that could change over the offseason as Mac has a year on Zappe in terms of strength/conditioning, etc.