I can answer this!
We don't want to put you at the MMR you think you belong at right away. Just because you've had a few good games, doesn't mean you belong at the high rank the system "Thinks" you belong in. Especially in shooters, it's very easy to have a few good games(or a few bad ones).
You see this, even in straight up Elo systems. You don't ever get put at the rank you probably belong, you have to play some matches to get to your true rank. In fact, if we did use the chess method of ranking up, technically using that rating system requires 1000's of games to get you to your correct "rank". That's in a game that doesn't have patches, new maps, new agents, etc.
So we need you to play game, to make sure we have a decent idea where you belong. After you play 5 games we have a "range" we think you belong at. We purposefully put you at the bottom of that range in Rank. This is because we would rather put you lower, letting you climb and prove yourself, then have you fail downwards. It's much better experience for you, and your teammates, if you overperform instead of underperform.
Five games is not enough to say you know exactly where you belong in ranked. So the game gets an idea, puts you on the low end, and then you keep playing games. The system will constantly test you, to try and see if you belong higher. You can skip ranks if you are very fair below where you belong, altho this is rare(but happens to immortal/radiant players a lot when climbing).
We've taken this approach because we need to be accurate in finding your rank, and try to slow down cheaters from getting to the leaderboard. We also need to validate your skill, because like I said shooters are often very swingy in terms of performance. You could be a Haven Jett one trick, but the moment you have to play a different map or agent you do awful. If 5+ of your first 10 matches were on Haven we have a skewed perspective of where you belong.
Also MMR systems, and why lots of games avoid showing you actual MMR, shifts wildly. One match you may get +1 another +10. You have no idea why you are getting +1 for one match and +10 for another. It doesn't let you set personal goals, or be able to know "If I win 5 matches I'll rank up". We prefer a Ranking system, living on an MMR system, because it's easier to understand and lets you focus on the important part - win the match and you'll go up in rank in X amount of wins.
At the end of the day, how we sell it to you doesn't matter. Just because we show you an MMR number, doesn't mean it's your actual current skill. You have to play tons of games to get your MMR to your actual skill. This is no different in our system, we just present it to you differently. You would still have to play the game, and win, to climb. Our goal for ranked is finding your true skill, and to do that we need you to play a few games. Even if we opted into showing raw MMR numbers, we would not want to display it until we were sure we knew you were at the correct rank for your skill. This is true of Elo systems as well, you would have to start at 0(or whatever base is) and climb from there.
devtrackers.gg