It doesn't matter. It stay in one place almost permanently. Even if it has a warp drive, but it's role is as a space station, and not as a star ship. Even DS9 can move like Star Ship. You can see it move when DS9 wanted to move closer to the worm hole. Plus, there is a very thin line difference between a space station and Star Ship anyway. What make them different is their role / job. So as long as Starfleet HQ role is not exploring strange new world, and stay in semi permanent way as a space station, then, it is a space station.