Well, even if true, it's still reporting third-hand information. The "update" is just someone trying to justify the reporting of gossip. Whether Bloomberg fails to deny it is irrelevant, and hardly a confirmation of truth if he doesn't, same as to whether or not there's a retraction. It's gossip all the same, true or not.
It probably is true, as most politicians are pretty dаmned arrogant to begin with, but that's not the point, and it's certainly not professional journalism, just as it's unprofessional for Murdoch to relay the contents of a conversation that he never heard.