I did more testing this morning, and my theory has been debunked by...Me!
I was trying to eliminate warping/route anticipation by my defenders so I was fiddling with reaction time/coverage/player speed threshold etc.
I let the CPU control Reuben Foster on my defense while I controlled another LB...With pass coverage at 75 and reaction time at 1, Reuben was with the TE but the ball consistently dunked off his helmet like he was oblivious to an incoming pass.
I put it back up to 99 and while the coverage didn't change, he saw the throw and intercepted the pass much more consistently.
So, while it was a fun theory for a minute, the slider isn't backwards!