Matchmaking around Champions

As a LeBlanc main, I see in tons of YouTube videos that there's almost always a LeBlanc in game. However, when I play a game, I rarely ever see another LeBlanc, even if I'm not playing LB. A YouTube commenter told me that Riot likes to queue people with other people based on the champs they play so that you don't get a lot of Mirror Matchups. Is that true?