We acknowledge that the game is a work of fiction. Historical fiction, but fiction none-the-less.

If every fifth character is also black, I think there is a point that can be made about verisimilitude and taking liberties; but since we know he really existed and that there has been debate on what he did, having a work of fiction that portrays him as a samurai under Nobunga doesn't seem unreasonable.

To compare, we know that Leonardo Di Vinci didn't hand out guns to people or build functional flying machines - but we know he designed all sorts of stuff ahead of its time, so it kinda fits in a fictional story with him in.

But only one of those seems to draw huge amounts of complaints online... And it's actually the less historically accurate one.