This is why I think the argument about applying overuse to all man-to-man plays is moot. Here's a density plot of the four most common normal defenses against the 113, 203, and 212 passing plays.
Criteria: Teams from USFL and NFL leagues that completed at least 50% of their passes against defenses NOT the Flat Zone. This filters out underperforming QBs against all the other defenses.
Note that the density for the Flat Zone is almost twice that of the others at ~0 yards. So the others are in parity but the FZ is not.

But, Seth, come on, you're surely skewing the data by looking at all passing plays.
Alright, here's just the short passes:

...and short passes with the 3-4 Cover 1 added.
