Well, I’ll be. Ignorance fought 
…which means that it resembles a barn turned on its side (with the floor facing the pitcher).
Of course, this is referring to a left-right or right-left movement. You could certainly clip off the tail end of the plate at the top of the zone for a strike (though I doubt an ump would call it a strike, as it’s moving far too fast for that sort of precision).
First of all, support this with some cold, hard evidence.
Second of all, even if there was an accelleration of curve as the ball slows (very possible), it is unlikely that that would do more than, say, double the amount of movement as the ball crosses the plate from the calculations given. .8" is not significant, either, and certainly isn’t what was envisioned.
Much more likely would be the possibility of a strike occuring where the ball was too high at the start of the zone, and dropped down into the zone on the way past the batter. Won’t happen on a fast pitch, and is very unlikely even on a slider, but an off-speed pitch could do it, especially if thrown as an over-the-top curve (rotation along the line of motion). Someone might want to calculate the delta-y of a parabola during the period of time over the plate under those circumstances.