I don't understand why people need to move in Z axis. Perhaps K3ph42 can explain this to me? As far as I can tell most guns have such turret coverage you can't go above or below the field of fire.
Not having played SoaSE, I can't predict whether the same tactics will be useful, but in HW, it was useful if you needed to hide ships from your opponent, sneak up on them, or if you were the type to try turtling in that game, you could pack more autonomous turrets in your 'base' without cluttering or obstructing your other operations by positioning them above or below things rather than only next to them.
Ships move in all dimensions, X,Y, and Z, but it is easier to control than the Homeworld style.
That's what I wanted to hear, thanks!