AS 100 legitimately receives from its provider AS300 in the zone a route to prefix |$P$| in AS200. If AS100 leaks this route to AS400, the route [which includes multiple AS hops (200, 300, 100)] will not be marked VERIFIED, and since there is a verified announcement for the prefix |$P$|⁠, S400 will not prefer the leaked route. The leak has no effect.