Agreed, I worry about this too. The Quest uses a similar gesture with hand tracking (finger pinching to click) and it feels really frustrating compared to the much more direct feel you get with the included controllers.
With the Apple you don't even have controllers available if you want them so gesture tracking must work perfectly. Apple does have a lot of experience in getting stuff like that just right, but I really wonder whether eyetracking + pinching is comfortable for hours.