If you want to flash the update onto your phone with the company's custom chip, you won't be able to do it with the old version of the operating system.
The notice warns of the anti-roll back version of the update for the devices. You won't be able to flash older builds on these devices after you've flashed a 13 build.
This is the best time for you to get out of the cycle of accelerated updates without wiping your device. You can unenroll once your phone has been updated to the most recent version of the software. You will get early access to test builds of future feature drops if you stay in the alpha group.
A new permission option to reduce notifications is one of the nice new features in the new version of the mobile operating system. The release is only rolling out for thePixels, but it is expected to hit other devices later this year.