Yes, it's a 34" scale bass, so it definitely counts as a long scale. It's also technically a
hollow body long scale bass; two smallish support blocks for the bridge and the pickup, aren't enough stuff to qualify it as a semi-hollow body. Which is why I own one. My 2 Danelectro DC59 Pros, OTOH, are
definitely semi-hollow long scales; which is why one of them fills the "Semi-hollow Body Long Scale" spot in my "Bass Herd". The other one fills the "Danelectro Bass" spot...
As for the JC Bass being a "top seller"? Well... Epiphone seems to sell the ones they make, but I doubt it's their top selling bass. Long scale hollow-/semi-hollow body basses do have problems; actually, pretty much the same problems that Thunderbird basses have. Lots of neck dive that, because of the body design - and that long, heavy neck - you can't do much about. And those upper frets are a
long way away, too. Slinging them way low, and playing with the headstock way up, is the way most T-Bird players solve those problems (and, so do I; I own 2 of the things); while it does look cool, it's not for everybody. And, T-Birds aren't Gibson's - or Epiphone's - top sellers, either... Comments from Gretsch White Falcon owners here on FB are full of complaints about those same problems. And, that's why Gretsch doesn't make all that many White Falcons - and never has...
So... while Epiphone does sell quite a few Jack Casady basses, and while I was also very pleased when they started making lefties ( that "Long Scale Hollow-body" spot in my "Herd" was empty for a
long time)? They still have the same problems that basses like that, have always had. And those problems have made many, many players avoid those basses...