Could be the fact that the skins are going on old planes. Which will be replaced. - I haven't seen what would happen yet where every plane in a large furball has a seperate skin. How much load does it out on ones system? Since the old skins have larger textures than the new ones - could be a sort of test to see what happens.
Then again I could be way off base and it's really just a matter or quality control.
Who knows, When the new models are finished, there might be a stricter enforcement of "what's acceptable" and possibly harder to get skins accepted due to quality demands.