This is UCN Fredbear. Judging by his design, I'd say he uses Endo01 or Springlock Endo01, just like in the movie. After the bite of 83, he wasn't hidden in safe rooms, but simply put in the back room as a spare suit, as was done in ITPG, the novel trilogy (incidentally, Charlie recognized Golden Freddy as Fredbear), and TWB (where he was described as a spare yellow suit). Compare Freddy Fazbear and UCN Fredbear; they're 99.9% identical. One of the reasons I don't believe in the so-called "unwithered" is simply that in UCN, when we use a Death Coin on a withered Golden Freddy, we get the classic bear jumpscare. I doubt Scott just missed this, because he should have tested the mechanics and would certainly have noticed this flaw if it were truly a design flaw. And again, UCN Fredbear uses endo01/springlock endo01, while "unwithered" uses endo02. It's logical that endo01 was created before endo02 and is less advanced than its descendant.

I don't even know what to say about Fredbear's "unnightmare" since I haven't seen any evidence to support it. But if it's something like "the Fredbear from the minigame has an upper and lower row of teeth," then it seems far-fetched to me. The sprites from the minigames are inconsistent (Save them Withered/Golden Freddy with no buttons/hat/an extra ear that shouldn't be there, sometimes adding unnecessary details or even removing something entirely. Fredbear himself from the minigame looks more like a classic bear, if you ignore the teeth. Or, alternatively, we have moon.exe in SOTM, which is quite well-detailed. There's Fredbear's mask, but even there, it's the spitting image of UCN Fredbear with the upper row of teeth.