@AriadneAnarchist@anticapitalist.party M-A isn't the One True Authority on what is and isn't metal (and doesn't claim to be). Some people try to hold it up as that, but they aren't worth paying attention to, imo. There are like 10?-ish people deciding what does and doesn't make it into the archives, so they can't possibly speak for the whole metal scene.
Metallum is a great resource for finding new stuff, and it's a good general guide for subgenres, but it's not the Holy Bible of Metal.