I don't think that practicing this way with a knife is bad at all from a motor skill standpoint, but it's not a major consideration overall in the scheme of things.
First you need to have a good reason in your mind to be using this kind of attack. Both in the sense that it's lethal force and must be justified, and - as far as you are concerned - there must be an occasion to choose this over an option such as tangling up with the attacker (with or without your knife in play).
To my thinking this use of the knife is a consideration in two circumstances, and both of them are mid-ranged. In terms of carryable type impact or edged weapons, IMO there are three distances - outside of range, mid-range, and clinched or close-range.
Without discussing appropriate tactics too extensively, and keeping it focused on the scope of the thread, I'll just point out that mid-ranged exchanges involving deadly force rarely stay mid-ranged for very long: people have a tendency to move toward or away from something that's trying to hurt them.
So the two potential circumstances I can envision using a knife in a mid-ranged defensive encounter are where someone else has a knife and you have a knife, and happen to be in the rare but nonetheless possible "knife vs knife" fight. This CAN happen but is unlikely. If he is semi-sane and coherent it could remain mid-ranged (sane people don't tend to close on a drawn knife).
The other circumstance I can envision is multiple potential attackers encroaching and you draw your knife ready to use it, but prior to using it in order to intimidate. This is maybe not an ideal use but again it depends on the situation.
So knowing those are, IMO, the two most likely mid-range defensive knife roles, the question is how would you use a "precision" knife technique? I don't believe precision is as much of a concern in a clinch - not hitting yourself and maintaining proper position are of much more concern and much more doable.
I know of three ways to use a knife - forward grip edge up (like a clinch pick), reverse grip edge in (Aka Pikal, like a disciple or spyderco p'kal), and conventional/forward grip edge out (like a kitchen knife, etc, with a locked thumb grip - no "perchy perching").
My operating system runs pretty lean whenever possible so as to not use up a lot of RAM. I like simplicity and feel that FMAs engender needless complexity with all of the learning of angles, etc. I prefer to work on footwork (not saying FMAs don't teach footwork), positioning, and combos.
I've found that an eye-shot is impossible unless you set it up, and the best way to do that is to go for a hand shot. I do NOT believe "defanging the snake" works with a 2-4" bladed knife from a physiological standpoint, but I'll take what I can get. Ideally if we get a solid hand shot, we can step in quickly and follow up with an eye, neck, clavicle, armpit, sternum, or temple shot. Again I'm not picky.
By far the most powerful method for me, used properly, is the reverse grip edge in, like this:
It involves a perpendicular hip snap (you step in with your lead/strong side foot and fire the hips so as to turn partially away toward your weak side) and usually full extension (elbow and shoulder turn at the last second while hips fire), which does leave one vulnerable unless done extremely quickly and to less than full extension.
The set-up shot is similar but with less extension and more circular.
The beauty of RGEI is it works great with things like pens and flashlights.
In both cases since the edge is inverted you can pull toward you and catch something other than your target should it be there.
I guess I rambled but what I'm getting at is that there is a lot more to pulling off a precision knife shot than just possessing the precision, and it's not a very likely skill to need, although that doesn't keep me from practicing it.
