Quit Rhythmbox from Natty Launcher does not quit

The mentioned bug reports are about Lucid, Maverick.
Regarding Natty Unity Launcher consider to report a bug.

Background.

- Quote -
And you might, or might not, want to keep playing music even when the music player isn’t open. In these applications there is at least a useful distinction between “Close” and “Quit”. Unfortunately, the result is that “Quit” is being used to mean several quite different and non-obvious things: “don’t check for messages any more”, “go offline”, “stop music playback”, and so on. A single term probably isn’t a good presentation for all these things.

In summary, then, “Quit” is more confusing than useful. For many applications, it can be either removed altogether, or changed to the more straightforward “Close” if that item isn’t present already. But for applications that run configurable things in the background, the design is a little more complex.

Music
.... players like Rhythmbox and Banshee, though, what should happen when you close their window has long been a source of debate. With Ubuntu’s sound menu, we have a chance to resolve it clearly.

Always be closing

Phone and tablet operating systems, such as Android and iOS, have abolished the ideas of “quitting” or even “closing” applications altogether. In Ubuntu, running on screens large enough (and with pointing devices precise enough) for multiple windows, “Close” remains a very useful idea. But with a little effort, we can reduce frustration and simplify Ubuntu overall, by making “Quit” something that humans no longer have to think about. Let’s stop being quitters, and start being closers.
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http://design.canonical.com/2011/03/quit/

Wiki SoundMenu says:
Rhythmbox should be altered to comply with the standard behavior: it should keep playing if closed while playing, it should exit if closed while not playing, and it should restore location and other state on relaunching.
https://wiki.ubuntu.com/SoundMenu#Rhythmbox