It can't have been designed because it used to be the same number for offense and defense, before the matchmaking overhaul got it bugged. (for a while it was also bugged for offense, but that somehow got fixed)
They definitely intend to fix it because Tin said he's pushing the team on it, but it seems it is just so far down the priorities list (because what we need is new pay to win troop tactics every week instead...) it takes half a year for such a simple thing to be fixed...