This is a good topic because it shows something about Metal fans and the insecurity we have when something is labeled outside of our holy genres and we feel it should belong to us.
Speed Metal is to blame really, for it started both genres. Speed Metal isn't a poplar term: it doesn't roll off the tongue well, it's not recieved well, and is trumped by the fictional "Thrash-Metal."
"Thrash Metal" isn't even passing. Bathory, Sodom, Amebix, Celtic Frost and Venom... they all belong to us right? BLACK METAL! Along with Slayer, Sepultura, Kreator, Exodus, Carnivore and Exhorder...right? DEATH METAL!
And it sucks...
I also feel this burn, but in the vigilance that is empiricism, it's best to go with accuracy. Proto-Death/Black Metal isn't really a genre, but more of a description of those albums' influence on what was to come. Those bands stated above (among many more) violently progressed Speed Metal into evolution. It just shows that their innovation and creativity was so powerful that the confines of that genre could BARELY hold that sound anymore before the threshhold would eventually break into a new genre.