Just to clear things up: This is even a “silver”-feature. You landing on Plat 3 doesn’t mean anything because you have two different mmr values with the invisible one have being lower than your visible one (the ranks).
You have forgotten the more informal quotes as well:
He never talks about the situation where it happens - and this is what the players document all the time: Win five games and lose suddenly five games with unfavorable conditions (Cho’gall against Malth/Tychus/%-based attack heroes for example to take him completely out).
It has nothing to do with skill when you have an extremely unfavorable game, the game tries to hold you down and rightfully so people call them out for the bad matchmaker.
What you experience is drafting, where it is more limited to “who picks right or has hero x to counter” which also contributes into the matchmaking, paired with talent habits (you can find a bit about it on hotslogs and the winrates for each hero). What people easily forget is that the matchmaker is a very complicated written code which attributes EVERYTHING what can be accounted for (winrates, talents, characters, maps, literally everything what can be calculated).
I’m glad that you made it out but you have to see good players yet.