The syncopation is still the distinguishing characteristic IMO. Syncopation in three or six etc. is slightly more confusing to hear than four. In 4/4 time, if you put accents on beat 1 , the- &- of- 2, and then on beat 4, there is an obvious uneven pattern to the syncopation which sets up your ability to easily hear the beginning of the next measure. You're taking a straight un- syncopated eighth note feel (2+2+2+2) and swapping it for something like (3+3+2).
In 3 (or 6 or 12 etc), it feels funny, because you're trading one kind of EVEN pattern for another, to achieve that syncopated sound. So, a 2+2+2 straight, folky waltz becomes 3+3. So, now more subtle SECONDARY accents are necessary to sell it ...or even to learn to hear it easily, but it's among the best stuff in music once you learn it. Of course all of this is easier in person. Very awkward in text form. I do this stuff with kids but it's incremental steps at a time. The kind of feel he's getting in that video is pretty advanced in my opinion. Great playing.
Here's my take on the syncopated bit. Still awkward. In lessons I'd break it down more for sure:
https://youtu.be/MBOic1ycags