The major league strike zone defined as:
The official strike zone is the area over home plate from the midpoint between the batters shoulders and the top of the uniform pants - when the batter is in his stance and prepared to swing at a pitched ball - and a point just below the kneecap.
That top part sounds like a real PITA for an ump to figure out. Bottom of shoulder or armpits or something sounds a lot more determinate.
We have to remember that the rectangle only depicts the front edge of the plate. The real zone is a pentagonal prism between the above upper and lower limits. I certainly can see why some of the breaking balls just above the top of the zone could drop over the plate in the zone and look high per the rectangle. I suppose a big breaking slider could so it as well.