The PCI toggle is just the yellow overlay that appears on screen showing your plate coverage. It doesn't appear on-screen in directional anyway, so it doesn't matter whether it's on or off. The only time you'll see it in directional is in the swing analysis window, and as I alluded to in RLB's post it still moves around under-the-hood even though you can only see the circle stay in the middle there.
And, even for Zone hitting the underlying system is still working whether or not you turn the display on or off. Even though you can't see it with the PCI off, you still move the hitter's plate coverage around with the left stick.