I, collecting the 'laxes, kept an eye out for it for years and never saw anything like it. Not in another's collection, not on auction, nowhere. Only ever that one image.
At one point I obtained a large Tomy Snorlax plush off Y!J. A couple years after that this post pops up listing Big Size Pokemon Center plush... including a Snorlax identical to the Tomy one I'd gotten. I asked the poster about it and they showed me the commercial from the NYC Pokemon Center to prove the Snorlax they had listed was indeed the 'Big Size' one. Mine was a later reissue of the same pattern, but apparently I'd owned a 'Giant' for years without knowing it!
Which leaves the question -- what the HECK is this neckless one? Is it possibly a prototype? Google image search only brings up that Pokemon Plush Project image. Ordering the 5 Foot Snorlax led me to revisit this mystery again.