We don't know wether the Global uses the SDF designation at all. The ship is only refered to as the "04 Global" during the episode. While that might be its designation, its also the designation the Megaroad ships use. It could be that after SW1 the SDF designation was used interchangably between new Megaroads and Macross class vessels (with the Global and the original Macross we know there were now at least 2 completed) If so, that would make the Global one of the first new ships to be produced after SW1.
Makes me wonder if any more will be popping up. Probably not but who knows?
PS: Hello everyone, longtime-lurker-first-time poster here.