I wouldn't be surprised if Nokia purposely leaked it to justify the delay to the community without saying "We can't release an update because we're trying to figure out how to make it stable". Nokia is most probably willing to take the risk with causing almost bricked phones because the ones who updated it would get the illusion that it's still buggy and they're still working on it so they would stop making bad press to the world that the N900 is a bad phone from its bad support.