Strike Zone: does the entire ball stuff apply vertically?

Say what?

Subtle strike zone change: ENTIRE ball must be over the plate. Wednesday, February 13, 2019 9:33 AM

The previous post deals with the ball horizontally, which is addressed in the rules. However, that same is not mentioned in the vertical definition of the strike zone.

Both the top and bottom of the strike zone are vague enough but neither mentions how much of the ball must be below/above the limits. It matters ... a lot.