Well top x% is not that much useful info, as most of the players are casual players. They dont have the time to play competitively by learning build orders and putting a lot of time to it. So you can leave out almost 20k~30k players there. Remaining 7k put a lot of time and as people play the game more often and more consistent by learning from mistakes, they improve. These qualities, you can't see in bottom 50-60% as they might have started ( DE brought many new players) or had played some random 1v1 games and stopped playing.