You can be a king or a knight or a nobleman or some other person of interest (or person of no interest) and have black skin. We have plenty of examples (as collected by the blog I now linked twice) of black people in lots of different roles. Hence, video games could easily include black people in whatever role they want and still be historically accurate (even though they could also choose to ignore historical accuracy). And that means that the choice not to do so is a choice to exclude black people. Which is a problem if it happens constantly. And it does.