That Sam Sweeney track is a perfect example of how you can "break the
rules" when you understand the music.

No, of course that performance isn't intended for dancing to - not in
the usual folk (or in this case specifically morris) dance sense any
way. But it sounds lovely. And it's a million miles from the drummer
playing 4/4 behind a jig presumably because he didn't know any better.

As for hornpipes in 6/8 - no, there's no history of that, but it might be someone confusing 6/4 with 3/2, and there were many 3/2 hornpipes in 17th and 18th century England.