That could be it. The gray knight does look like Odin, and Odin often dressed in Grey. And the Black Knight, does look like Cul a bit - black hair and beard.
I think the writer may have misunderstood a bit of Fear Itself tho' - in it, it was said that the era of Cul, existed MILLIONS of years ago - the Chosen even remembered the Dinosaurs! And apparently Odin killed all of humanity, in order to remove Cul's influence on them. So, I suppose the people he killed, if they were around millions of years ago, couldn't have been humans, but rather, something very similar.
The humans in this story, are obviously hominid, not fully evolved into homo sapiens yet, and unlike in Fear Itself, there's an Ice-age going on, instead of perpetual summer. This story seems to only take place maybe 50-60 000 years ago, or something. So that can't be it.
Well, the writer could be retconning it as well, we'll see how it ends up. Fraction retconned stuff too, so I guess it's ok.