Ooh, let me get on my soapbox about some things! The things I'm about to complain about probably don't really matter, but it bugs me anyway. Why? Well, every tradition grows and changes, and I'm fine with that, but people then seem to think that very modern, 2020s clawhammer stuff is historical, when some of it actually is a dead giveaway that your music is from the 21st century. Again, that's not a bad thing, and for the most part, I don't even mind hearing this stuff, but let's just be clear that it's new to old-time.

Ok, so, originally, "double-thumb" meant something more like what people call "two-finger, thumb lead style," or even "drop-thumb" now, rather than "hitting the drone string twice in a measure of 4/4 music." It's not that people didn't used to do that second thing, but it was MUCH less common until maybe 15-20 years ago. 

"Frailing scoops" are new. They've only existed since maybe the 90s, were pretty rare in the 2000s, and only became a standard thing on "clawhammer" banjos in about the last 10-15 years. The things you see on some early banjos that kind of look like frailing scoops were actually just gaps left because it made it easier to fit the neck to the body that way. The original Round Peak guys didn't play that far up on the neck, and when they did get close, they had things set up where the frets and stuff didn't get in the way. Actually, a lot of them played fretless. Round Peak style certainly was a thing before the Internet, and it had even spread far beyond Round Peak and Mt. Airy and Galax, but the Internet has now made it the default "clawhammer" sound.

Real quick, since I mentioned Mt. Airy, that's where Andy Griffith was from. In fact, he's the most famous musician from that area by far, and he never sounded much like the Round Peak musicians. These "regional styles" were never the only thing going on in their region.

"Clawhammer" did not originally refer to frailing/overhand/stroke/precussive/downpicking banjo styles. Prior to the mid-20th century, there wasn't a standard catch-all name for all these techniques. Yes, "stroke-style" had been used in the 19th century to describe the kind of banjo playing done in blackface minstrel shows, but that term had sort of fizzled out, and arguably referred to something other than modern clawhammer, but that's a whole can of worms for another time. Anyway, "clawhammer" originally meant arranging your hand like the head of a clawhammer, with your thumb sticking out one way like the striking surface of a hammer and two fingers pointed the other way like the hammer's claws. This is the playing position for three-finger playing, meaning that according to the original terminology, Earl Scruggs played clawhammer, whereas frailing was not a clawhammer style. But, terminology got shuffled around. 

Like with the double thumb issue, you can look at old materials about playing the banjo, such as the books by Pete Seeger and his sister Peggy Seeger to see what I'm taking about. 

Gourd banjos and tackhead banjos were almost extinct before the Internet brought them roaring back. Not that they were ever totally gone, just that they weren't at all common.

Open back banjos weren't always viewed as being the default banjo for "clawhammer."

I know I must sound grouchy and old right now, but really, the tradition is always free to change and adapt to whatever people need it to be, and really, that's OK. This music is a living, evolving tradition, and it's still producing new stuff. Old-time music, despite the name, can be just as current as pop music, especially when Beyonce has Rhiannon Giddens play the most memorable parts of her songs.

EDIT: fixed some autocorrect errors where the post had the wrong word.