I have problems believing anything that comes out of Amon's mouth. I thought his energybending was fake. Even if it is real, now I think he's a bender too which is how he's capable of bending energy. "Amon" is a chosen name, a title, and his backstory is made up to gain sympathy. Random firebender aggressor? Who wouldn't believe that? Everything about him is a lie; a story serving as an identity cover. So yes, that is indeed a scarless, non-burned face.
Amon © Bryke