Think of it this way. There are people that did better than him this year, obviously. But for b1t not make top 20, that means 20 players were better than bit this year.
Looking at the navi achievements this year, b1t's stats at the big tournaments and lots of maps played in the big events and playoffs, there are not many players that did better than bit.
Sure, some players have better stats than him, but they have low map count played at the big events, so this fact will at least put b1t in top 20