Except that it does work like this on a regular basis. It's not just something that sounds nice in theory. Distros and other major software vendors regularly coordinate disclosure. Have there been failures of the process? Sure, but that's the nature of secret keeping. The advantages of coordinated release far outweigh the risk of occasional mistakes, since the latter simply leaves people in the same position as they'd have been without any coordination (i.e. the exact same position that the distros were in with heartbleed).
