CiG
Approximately Infinite Universe
I'm not saying that calling black metal alternative metal is an established usage of the latter. I'm saying that by the definition of alt metal, a lot of black metal should count if there's to be any consistency. My argument stands; music indistinguishable from black metal in terms of riffing, pre-dating established "black metal", exists, and it came about by and large in the alternate scene.
If there's to be any consistency, Black Metal shouldn't even be a genre, because the bands that fall under the category often sound very different on a technical level.