Guitarists have a history of appropriating banjo terms and giving them arbitrary meanings. In "Guitar Man," the author mentions Bert Jansch describing a technique where you keep an alternating bass with your thumb while using two fingers to hit pairs of strings on the off-beats as "clawhammer."

I think Carthy's accompaniment is fine, although I find that pattern just about impossible to play consistently. My fingers are used to something a little different, and they try to revert to it any time I'm not strictly minding them. I think if he were to play it nowadays, he'd probably outline the melody in the bass and then fill with snatches of melody or counterpoint, since that's basically what he's done on most songs since the 70s or so.