So I tested Ranked placements using 2 new accounts, one that was Diamond 1 in controller and had played a lot of social and one account that was completely fresh. (My apologies for everyone on my team during these tests but I really wanted to know what was going on with all the funky rankings people had been getting)
I sandbagged every game, going 0-15 or 1-15 as much as possible, bottom of the team. On the account that was fresh, I placed bronze 1 and played vs completely brand new players the whole way through.
However, on the account that was Diamond 1 in controller queue, I placed gold 6, despite doing significantly worse (0-20 to 0-30 because the players could actually kill me). I also NEVER played vs worse players, despite performing abysmally the entire time.
So basically, your ELO transfers between ranked playlists, either from social or from the other ranked playlist. I had wondered why my placement matches were so difficult despite having played no ranked at first, but it turns out that’s why.