Certainly not impossible, or even unlikely. The overall build doesn't really look like a Punisher product, but he's been out of the game for a while, and any number of mods might have been done to it since.
For that matter, it might be that Pun just did the milling and anno, and sent the parts back to the customer to be assembled. I've done that kind of thing hundreds of times...
Many years ago, and several computers ago, I had a folderful of modded markers, mostly 'Cockers. There were hundreds of pics of one-off 'Cockers (or just bodies) done by any number of garage-shop airsmiths. Rhino Joe, Miscreant, Timberwolf, White Wolf, Brad nestle, Jeremy Garrett, you name it. There were a handful of bodies done by a guy called "Dive Rat", who, it seemed, had made it his life's mission to see how fancy he could make a 'Cocker backblock.
So there's thousands of 'Cockers (and Snipers) out there that were heavily customized by some random Joe Blow, who never got "famous" enough to have a recognizable style, and who has probably long since quit the sport.