I mean, what BB is going after is clearly not Pluton. He and the Marines are fighting over "something" and that something was in the newspapers 2 weeks prior on the timeline, if that's the case, the Marines and BB would have been at Wano already.
And because Oda has kept Caribou's mysterious person anonymous, imo, its not BB either because it's the obvious choice. This is the same deal with Shanks and the Gorosei too. They don't mention the pirate by name, but people expect it to be Blackbeard by obvious association, which i think is wrong