Agreed, the range does matter. But for airsoft it's not much of an issue.
Even at long ranges, center of mass makes sense because you still have a lot of leeway in all directions if you aim for the center. The way it's described; if you shoot low you hit the ground. If you aim at center you will at least hit the lower target area or the upper area, or side to side.
It's far simpler to show than to describe.