I haven't read whatever happened in Aquaman, but the African heroes thing was a bit more plot essential. At least as an explanation as to why the continent is superhero free except for Batwing. Nevermind the usual condescension of Africa being some kind of actual entity, but whatever.
The difference being, at least from what I can tell not having read Aquaman, some character was introduced in Aquaman, then killed off. In Batwing, they were all already dead at the beginning of the story, we just eventually saw it happen. For that story, you needed dead superheroes. And it would have been really weird if they were white.