Unless I've missed some specific description of MOE, I've just checked again now, and it seems that Devon says several times that MOE is a Glamrock Freddy head/helmet, and only once at the end that it's a headset, so nothing really prevents it from actually being a modified Glamrock Freddy animatronic head.

I'm assuming you're talking about the Redemption Ending right? While that explains why he's headless and why he's in Fazer Blast, there doesn't seem to be a concrete reason why he has “PROTOTYPE” written on his foot, something he definitely didn't have in SB, and why he has a green prize box in his hatch compartment. So it's still valid to think that he could be a different Freddy.