This is soley for show/ making the climb harder
A silver 2 player on a win streak will play gold 4 (because on a mmr ladder he would be gold 4)
Or a silver 2 player on a loss streak will play bronze 5 (because on a mmr ladder he would be bronze 5)
It has its gives and takes, but for me personally it just makes me play people above my rank in hopes to reach their rank, which is pure bullshit.
Leagues match making is based on an outdated 1v1 chess algorithm, that doesnt factor skill level or teamplay.
Elo, glicko, and glicko2 do not perform well enough on "TEAM" games of skill. Sure its close, but it puts good players on bad teams and vice versa.