Iirc the N900 was available in many more countries from the get go, but was held back in some because the OS and software wasn't really ready yet.

With the N9 it seems more like: the device will be ready but is kept out of retail channels due to the strategic alliance with MS; i.e. they want to push WP7 there. (I'm basing this mainly off how Elop tries to downplay Meego and praise WP7 whenever possible)