Rap music doesn't have its origins in Africa anymore than rock music does.
They're African-American in origin. African, sure, but very much 20th century, out of urban environments in the USA.
The 20th Century is a blip on the radar for Wakandans, totally insignificant. New, western, inferior & foreign. They're as dismissive of foreign African people as they are of foreign Caucasian people.
As a black guy, it just bugs me pretty seriously. If the actual score by Goransson wasn't so good, it'd be a lot moreso. But given the score brings the African stuff in spades, whatever, let them have their cynical marketing tool with the hippity-hops. It's fine, it's inconsequential, Wakanda gets their actual representation in generous amounts despite the rap.