Huh. My memory of Nyambe was that is was very much intended as a D&D setting, with orc tribes (with a much different flavor) and the rest. And I'd even intended to drop it in to my game. But I'll admit it has been a very long time since I looked at it. I just remember really liking what they had done.
You could, and if you did, most wouldn't notice. But it would be culturally anachronistic relative to the fantasized versions of cultures typically found in D&D (and other FRPGs, FWIW).