I can can see how this can work two ways, and might vary quite a bit from player to player.
a) Never had much of an issue with it, and as soon as you start thinking about it, your game gets thrown off... the old "paralysis by analysis" rears it's ugly head.
b) As anhyzer says, kickers take very deliberate steps to place themselves "just so" relative to the ball prior to a kick, and trying to be as consistent as possible with the placement of their plant foot. I can see practicing this until it becomes 2nd nature. Just developing your routine so your always doing the exact same thing. Problem is that disc golf doesn't allow for the same surface and consistency of situation that placekicking does. Our lies aren't always on even ground, and may involve other factors we just have to "deal with."
I guess I'm just aware of where I placed my mini on the ground and go. I definitely plant my front foot quite solidly, so there's not much debate over my point of support when I throw, but don't think I'm one of those who cuts it that close to my lie... probably several inches behind, but not so close that I've ever been called on it. I'd be surprised if there wasn't a reasonable amount of grass clearly visible in real time between my lead foot and my mini/disc.
IMHO, if you really think another inch or so is going to make a difference on hole that's x-hundered feet long, you need to work on your mental game more than your mechanics.