My iPad 3 is pretty much "the Reflec Beat machine" and while it does have a timing adjustment option it only moves the moment in time that it uses for judgement. If I delay it to compensate for wireless earbuds then it will be visually delayed too past the judge line. Sure they can compensate for this with more options but I like sane defaults. I have never had to touch this slider because zero is already perfect, and in games with separate audio and visual lag compensation options I'm never confident that I've gotten it accurate. This isn't something you should have to ask the user to do.
https://i.imgur.com/qU2TEP5.jpg
