As called by human umpires it’s 2-dimensional. We have all seen the graphic where the catcher sets up on the edge of the strike zone and a breaking pitch, by the time it hits the glove, is clearly off the plate. But on ocassion they will show an overhead shot and the pitch clips the front edge of the plate.
Umps are like hitters, too. They can only really track the pitch to a point just ahead of the plate. After that it’s an educated guess.
The strike zone is 3-dimensional. You can argue that it is not, but you would lose the argument.