If you have fixed media (as opposed to realtime dynamically generated or streamed etc) this trick can go a very long way - or even if it is generative, if the time is used to drive the animation. It just requires good clock sync, like you said, which can be non trivial (especially if audio is involved where desync of even 20-30ms becomes very noticeable). But yeah, with NTP/PTP you can get v v far.