If you read the context of that quote, someone is asking about why the devs have implemented 2 matchmaking pools.
That is, categorically, 100% designed by the devs intention.
Has nothing to do with random chance… which is why Kerfuffle made an entire Q and A to address questions for what they did in their game.
What THEY did. Not ‘random chance’.
It’s the same system for both MMR and Rank pools to ensure balanced matchmaking.