They're real, in use, and for the meme. This specific subgenre of heavy music is very self-aware and at least 30% tongue-in-cheek, while at the same time being serious. It's a lot more fun and a lot sillier than it appears from the outside, I promise.

It's sort of like that discourse that happened awhile ago about the difference between "camp" and "tacky"; this stuff is strongly camp, just its own kind of camp.