This is strange: you buy a jet-black phone so that it looks slick. Then you buy a case and change its appearance because scratches might show? Weird logic.
The "9 step polishing process" is pretty much how you'd polish anodized aluminum to that level anyway.
(I do a large amount of machining).
Anodizing does not make it actually stronger. The layer it generates is slightly harder, but still do not have great wear resistance
There's not much you can do about this as long as you use anodized aluminum.