Why are we now getting punished for people leaving?

http://i.imgur.com/ehCu5Cb.jpg

I thought if someone left (without a team forfeit), that you didn't receive the loss. Lately, if someone leaves, I've been able to leave without a MM penalty but it's still giving me the loss.

eg. I won 3-4 games in a row, remained at plat 3 div 3. We had a PS4 teammate who left after one goal was scored a minute in (he clearly wasn't afk, just rq), so I left too. Started a new game (per the image, we won), and I division down.