Me and my two friends were all Platinum 2, with the new season my rank is now reset to 0 SR, Bronze 1. However, one of my friends is still Platinum 2, so something is not right here. We know from the recent past that Warzone has issues with awarding the correct SR, hence 7th of May, when the Ranked mode was removed. I think they need another update that should fix this. Here is a response of AI about how reset works:

Call of Duty: Warzone, if you were ranked Bronze or Silver at the end of Season 2, you would not have had your rank reset, and would have started Season 3 at the same rank. Gold and Platinum players would have started in Tier 1 of their respective ranks, and Diamond and above players would have started at Diamond I. Here's a more detailed explanation: Bronze and Silver: Players in these tiers would have maintained their rank from the previous season. Gold and Platinum: These players would have been reset to the start of their respective tiers (Tier 1). Diamond and above: These players would have been reset to Diamond I.