Wrong on many counts.
The Last is canon because Kishi conceptualized and wrote an outline for the story; he has no part in the writing of the novels and because of that, it is not canon. It's not just about publishing either; it's a whole franchise. He's signed over rights to use the Naruto name, story and it's characters; they can do and publish what they want - this is about his contract and law. He's never even "approved" any of these novels and even if he had, that does not make them canon.