It doesn't work. The arena should match by BP not by arena rank. BP determines who you can beat and have a good match with, not arena rank. And since ideally you'd have a 50% chance of winning AND a 50% chance of losing it makes no sense to lose points when you lose because ideally you'd be losing half the time if the game was balanced and you were matched with opponents with equal skill and BP. It is clear the devs put little thought into Arena.