I can’t speak to how Halo does it under the hood, but it’s very common to have a separate skill rating for unranked and to just not surface it, which is exactly what you’d want here, since that’s what prevents the brand new player from getting decimated in their early matches. You’re saying that the social playlists affected the same ranking as the competitive modes? That would be strange. In my experience though, a lot of new players bounce off a game when they get matched against people who are only marginally better than they are, which can be a matter of that other player understanding one thing that the loser does not. I’ve seen people call their opponents smurfs, and then when you check the replay, you realize, no, that player really is only a tiny bit better.