Is Spock Vulcan or Vulcanian? Were the Klingons conquered by the Federation, or just became allies?
That's just a difference in terminology. I don't think using one precludes the other one from existing.
Good point. The Vulcan vs. Vulcanian one is particularly lame.
Tell me, what is Kirk? A Man? A human? A Terran? A Homo Sapien?