As far as I understad, initial ranking was done based on calculated collection strength. Not sure how initial ratings were calculated and whether they were even different.Anyone know the milestones ratings when you get a rank up? I've gotten to 1971 and I'm still gold 1. A few fighters I've faced a few diamond 4 fighters and they were lower rating than me. (I'm guessing I have to get 2000 for diamond 4?)
But if you look at the rewards page it's pretty obvious that based on the season results new ranks will be assigned to players based on their relative performance measured as their ratings at the end of the season. So player with the highesr rating will become Legend, top 1% rating players will become D4s and so on and so forth. Not tied to specific rating numbers but rather relative performance compared to all the participant, similar to PFs.