There is always an advantage when attacking second, the original poster is correct on that. If I see someone failed 3/4 times on something in my D then I know I can two shot something of theirs minimum. That extra knowledge is advantageous. And some people do have GAC end in the middle of the night so must go earlier. So they are disadvantaged.
If the devs want the game to be fair while competitive it does make sense to hide it because it stops people doing 1 battle and quitting if they know their opponent did a full clear. But I agree that knowing I can skip GAC because of this is helpful for me to not waste time.
Maybe a compromise where you can see zones defeated but not the overall score? That way people know early if it's viable to try attack but not if they need to be 100 clean while doing it or if they have leeway.