lol it was definitely him. Always thought that theory was weird
we know that he's from a celestial dragon family, Sengoku stopped the war because it was him, Shanks has access to privileges that no pirate does.
He also came to the Gorosei to talk about "a certain pirate" that's definitely Teach.
And if it wasn't Shanks, and instead it was his brother "Fhanks", why would the Gorosei tell a Holy Knight that he "should have nothing to do with politics"