My guess is the latitude is offered for consistency. These pitchers have an approach in coming to the plate. There's no deceit if they do it every single pitch (or, at least, in Garcia's case, every pitch with no runner on base - he doesn't do that whole thing when there are runners on base, go figure).
At any rate, with Gausman, if it's a balk every single pitch, well, then, by all means. call it - every single pitch - and make him stop; otherwise, it is curious when an ump let's it go all game and then, out of the blue, decides to call it and it just so happens to coincide with a critical part of the game.
It's like a plate ump's strike zone - each is entitled to call their zone...just, once established, stick to it. Don't be calling ball all night long, and then, when a batter is patiently working the at-bat with runners in scoring position and down one run late in the game, that same pitch all of a sudden is a called 3rd strike to end the inning.
