Because you're approaching it with the attitude of making only 3 songs out of 9 "passable." You're shooting for baselines.
You put way too much stock in the "1/3 of the tracks need to be passable" thing. That is not a hard and fast rule; it slides based on the total number tracks. If you have an album with 42 tracks on it, having 14 "passable" tracks is fine, because it's fourteen, which is a lot.
That said, your implications about genre are entirely off-base. We're not going to reject an EP because it's black metal, or because it has 3 different genres on it. That's not part the equation. You say that you'd have the rest of the songs as good black metal, but not like "that," which means you don't think OCR would post black metal, which isn't true.