It looks like all the time near extreme heat reduced the bloat around his skin that was on display in JGTH, the heat also turned his skin into basically a leather or jerky.
I'm not really a fan of the perfectly symmetrical face, as was said previously, the deformity and irregularity sort of was a staple of the character.
However, in a sort of afterlife-lore, isnt your spirit supposed to be freed by the bonds of mortality? You know, if you were deformed or maybe had a missing limb in life, in afterlife your 'spirit form' (for lack of a better term) would be the way you were always meant to be. I mean could you imagine showing up in the afterlife and still being in a wheelchair, or with crutches or a debilitating disease? Maybe this is meant to be the pure version of Jason's soul that ended up in hell, only to be roasted by the fires and demons of hell for ages until this husk was all that was left.
This would sort of explain why the damage to his body and face is inconsistent with his injuries in the series, but his mask retains the damage from before.
I think its cool to look at it, and sort of like alternate universe Jason. More options isn't a bad thing when it comes to character selection.