His mask is just different because he is now controlled by Funtime Freddy since Baby was ejected from Ennard for being too egocentric in the other souls' eyes so then she rebuilt herself using parts from the sister location facility and now she is her own entity once again in FNaF 6 and separate from Ennard.
And I thought people couldn't get more ignorant Looking at the blueprint of Molten Freddy in the insanity ending, he has 3 "tags" active: Funtime Freddy, Funtime Foxy, and Ballora. It seems like the perfect recipe for Ennard, but Baby is absent, which is why Scrap Baby exists. Scrap Baby is Baby after being "ejected" from Ennard. After Baby's ejection, Ennard becomes the 12th Freddy clone in the series: Molten Freddy.