Isn't that page for Panther? What makes you think this feature is going to be implemented in a future release of OS X?
Sorry, maybe it was this sentence: "We plan to provide tear-off menus in a future release of Mac OS X..."
However, that doesn't mean they still plan on doing it. That was written some time ago now, and I'm pretty sure tear-off menus aren't in Tiger. Personally, I would prefer they stay out--I don't see much of a use for them.