They did and made a huge post explaining the matchmaking and how it works like 4-5 yeras ago or something. It was even posted and pinned here, but I can’t find it. If someone would please share that again, I believe it was AzJackson who posted it.
EDITED:
Found it! Here
Because of low playerbase. There’s just not enough players for a fair match, specially when the matchmaking still has to consider not only mmr, but also groups, roles, somewhat fast queues etc.