Not region specific; the same happens in EU.
I'm beginning to think that ranking up beyond diamond 3 is easier in solo queue, than in premade squads, as you usually face far easier opposition.
I just don't think there are enough players to get full lobbies of diamond and up each game. The wait times would probably be like half an hour for that to happen. So they have to lump in the lower level people just to keep wait times down. If they had cross play enabled you could maybe get it to work but without cross play (or one of the other BR titles dying) I just don't think enough players are in that bracket to allow for better SBMM.
