Maybe that’s true for M3s but isn’t true overall. My 2017 MS 75 received 2022.20.7 yesterday (and was on 20.6 before that).Are you on "Advanced" on the software page?
Also - looking at TeslaFi I can't see any pre-2021 car on 2022.20.6 (or .7). Must be something unique to the hardware configuration for those cars that this firmware targets.