Very simplistic TLDR now every action will be timestamped and when the server processes a tick it will play out the actions it receives in order and decide if any actions should be ignored, like for example if that player should have actually died before pulling the trigger.
I always thought that's how CS:GO servers worked, but apparently not! It seems pretty obvious and a very good solution that solves all of the problems between 64 tick and 128 tick servers in the past. Valve just continues to be a pretty amazing innovator in the world of gaming, you love to see it!