I said they are a sub-genre, never said it was dead on horror but it still a difference, otherwise they won't classified as a subgenre, besides I'm drunk, I can say what I want.
My point still stands though, Covenant is a slasher rather than intelligent horror, to clarify for those who don't see the difference... Covenant is more like Friday the 13th whereas the first Alien was like the shinning or the thing.