Linux

That's purely reaction with not even a countdown, plus whatever lag introduced by the browser, display, mouse or touch, phone or pc.

With music games you aren't waiting an arbitrary amount of time, you are matching a tempo and moving ahead of the actual sound to land on the correct time, almost certainly with visual cues that let you read ahead, and getting scored on how perfect it was. More often than not it will be a song fully memorized and the player is trying to push the limits of how close a human can get to perfection. There is still latency in rendering and display, audio playback, input, etc. and you can end up with visual cues being offset, input being offset by a different amount and direction, and as a result scoring being incorrect.

If a single human can't do that, then how would an orchestra ever have worked? Its different movements and visual cues but basically the same thing: Match timing with the conductor and between memorization, practice, and the sheet music you get your read ahead of how to move. I've never taken dance lessons but it surely comes down to the same fundamentals.