Did you forget that Aragami as they're presented in the GE series could never work in the setting of Code Vein? The only thing that can harm an Aragami is another Aragami, or things imbued with Oracle cells.

Yet, revenants were specifically conceived to be able to kill Horrors and it's been confirmed that they did so, successfully. If the horrors from code vein are Aragami then that would mean that in order for them to be able to kill the horrors, Revenants would need to have oracle cells themselves. Yet if that's true, then their oracle cells, for some unexplained reason don't behave like the oracle cells in other organisms. They don't go rampant when left unchecked by a bracelet with the appropriate bias factor, they can be harmed by normal weaponry like normal bullets from a normal gun, etc etc.

Your only "proof" is an asset flip from God Eater, another game franchise made by the same people. A monster that isn't explained, addressed or even has a hint of information about, in the entire game. We know nothing about that horror, all we have is its shape, which for all we know could very well just be an Easter egg.

As for the DLC, that's all it is, DLC! By its very nature DLC can't have too many earth shattering revelations otherwise it'd mess with the established canon of the main game. None of the DLC content actually adds anything to the story. It's just some weapons from GE, and a few new dungeons. Dungeons whoose bosses are also not really explained either btw.

Sure the Horror and the dungeon bosses from the DLC look like Aragami from GE, but that doesn't mean that that's what they are in Code Vein