Matchmaking algorithms cater better in higher elos
I don't know if it is just me, but I climbed from Silver 2, to Plat 3 this season, and the lower elo I was, the less chance I was getting my preferred role, I was more likely to get my secondary role or get autofilled, however, in higher elo, I am getting my main role more than 80% of the time, I don't know if anyone else has noticed this.