As maps get harder, player reliance on peripheral vision increases exponentially. Many top players scarcely even move their eyes all that much away from the center of whatever pattern they're in the middle of. The problem isn't in VR products or any form of technology - the fault lies in the fact that eye-tracking technology follows simply the positioning of the pupils, rather than what we are actually mentally focused on - that is something that is, if at all even possible, centuries of technology away from the present (as it would basically be mind-reading technology).
Humans view the world through a screen that we can only see about 2% of at a time - our brain automatically fills in the rest from extremely blurry data that is often mis-matched but automatically written over by instinct. Our vision is about 120 degrees, but our specific vision - formed by the
Macula, is only about six degrees in any direction, or in other words, about 2-3 inches in diameter on the average computer screen (which is about 6-8% of total surface area, by rough guesstimation).
At lower levels of play it can certainly seem feasible to follow maps with direct eye movement as the spacing between notes is often within that point, but as spacing and speed goes up, it becomes impossible to keep up with moving your focal of vision to every new note, so you fall back on muscle memory and instinct along with just plain practice at relying on peripheral cues - this is why some things are "unreadable", because they aren't following the standard rules that automatically crop up as player habits evolve to fit higher difficulties of challenge in this game.