It's one thing to say, "You have to back up your statement in the article on lawnmower racing that says that Peyton Manning is the world champion lawnmower racer." It's another thing entirely to say, "The onus is upon you to prove that we should even have an article on lawnmower racing in the first place."
I think it pretty much the same thing. Having an article on a subject is a statement that the subject is notable and verifiable, and the burden of proof is on the person making that statement.