Yep, it does avoid sync issues... well, partly. It doesn't know anything about the audio as that is handled by a pretty high level library. But it does make sure the frames goes at the speed they should. So assuming the audio isn't lagging behind or ahead (which I haven't encountered yet), the image and audio should be synced.
I think that playing YouTube in the terminal today is just a fun idea because the videos look so goofy. But like people say... Sixel... Everything is apparently possible!
Someday, somebody will make the whole YouTube platform.