“As you compete, your selected role or Open Queue skill division will increase or decrease after you complete 5 wins or 15 losses (whichever comes first) based on your win record, frequency of play, and the skill levels of your opponents.”
I’m at work so I only had time to skim. Idk I might be reading too much into it, but I take that to mean that the difference in MMR between you and the enemy team is taken into account in addition to win rate. I thought they said something similar somewhere else but I’m not 100% sure.