I don't see what exactly this proves. Old English was at least very restricted in color words: words signifying brightness and darkness, however, abound. (We students never knew quite how to translate fealu, "yellow, tawny, dun-col9ured, grey, dusky, dark.") I read years ago that number was always a late development in language. Not sure what fiction or creation myths have to do with language per se.
I assume they think Chomsky's theories about deep structure and surface structure are disproved, but without more information (lots more), I don't see how. Did Chomsky claim that all languages exploit every possibility of meaning? That would be laughable on the face of it; there's no reason they should, any more than every language must uese every phoneme the human vocal apparatus is capable of.
Also, regarding the apparent lack of fiction (I assume they mean traditional stories and myths rather than modern realistic fiction, which was a rather late development) and creation myths, I seem to recall reading numerous times over the years of primitive tribes who are more than capable of keeping things they consider important from outsiders.
I'm not buying that for a quarter!
I am supposed to believe that primitve hunter-gathers living in the midst of a major river system don't sit around the camp fire talking about their fishing skills & their sexploits?
I think that Chomsky was saying that the whole of language exploits all of the range of possibilities of Language.
I agree with you on Old English but a lot could be taken from context for example, Homer, Wine dark sea, no color there, but everyone knew what color wine was.