I always took the term as meaning that the ball was on the black border, which is most likely a strike anyway, as it is probably catching some of the white part. I don't think umps are intentionally calling strikes that catch the tiniest bit of black but not any of the plate. I am skeptical that any ump can truly get that level of accuracy correct in real time.
When you watch the games with the permanent k zone up, it is pretty much a crap shoot whether a ball that catches the sides of the zone by less than a third of the ball to the balls that are a third of a ball outside are called strikes. It would be nice if they could at least do something about the ball calls where the whole ball is in the zone or the strikes that are half a foot outside. Those calls can have really affect a game. They seem to be getting more rare, but they still seem to happen with some umps more than others.
You certainly bring up several good points that I don’t have answers to.
What I do know about umpires is they all WANT TO CALL STRIKES. Whether they’re trying to speed up game times, or simply wanting to get out of the heat and humidity then home to their families, umpires want to call strikes.
Back when I was catching many years ago (when dirt was just invented) umpires would often make subtle comments to me before game time such as, “I have an early dinner date with a very pretty redhead” or, “if you’re selling, I’m buying”. These hints basically meant any pitch 2”-3” off the plate when framed properly, will be called a strike. If you “sell the pitch” to the umpire with a nice frame job, he was certainly going to “buy” it with a strike call.
IMO Some games need to be helped along by an umpire widening the strike-zone and they usually are at every level but the Big Leagues because of this automated strike-zone calling them out.
I’ve even been at minor league games when baseball scouts have hollered out to the umpire, “get this freaking game moving, I have to be in South Carolina by 6 o’clock”!
Go Nats!!!