Come On Irishmafia dont give up on us now!
The strike zone is defined by physical attributes which everyone has. The sternum is ....well, let's say I'm not a fan as it is not a visible reference for an umpire. It is basically a guess and may vary from one umpire to the next. But then again, so can everything else
I consider it as a pass for umpires to not be harassed for not calling "the book" zone.
For those who love to refer to "the letters", that is another variable that if ever documented that way, you will see players with team names on their stomach.
Umpires are instructed to call bring it down a little bit (make the entire ball be below the armpit), up a little (some of the ball above the knee-remember, the zone use to include the knees) and spread it out a little bit.
This is supposedly done because the high and low corners are not the easiest for the batter to hit. The "area" of the strike zone is the relatively the same for the pitcher, just not rectangular.
And a lot of people concentrate on the catcher's glove position, but forget about the movement on the ball. They also forget (or are not aware) that the ball only needs to catch any part of the plate (including the black), not necessarily the whole plate. Meanwhile, you have idiot coaches that teach the catcher to hold the glove even after the call. Not a smart move. The call should be made by then, so there is no purpose other than to show up an umpire.
Consistency is important, including game to game. The only issue there is occasionally you get a catcher which doesn't give the umpire a good view by jumping around and shifting at the last second and the umpire ends up moving to see the pitch and in doing so, doesn't get the same look as preferred.