However, for Pixel 6 series owners, Android 13 is essentially a permanent upgrade, as there’s no way to roll back to Android 12.
With Android 13, however, Pixel 6, Pixel 6 Pro, and Pixel 6a are left unable to downgrade back to Android 12 builds.Warning: The Android 13 update for Pixel 6, Pixel 6 Pro, and the Pixel 6a contains a bootloader update that increments the anti-roll back version.After flashing an Android 13 build on these devices you will not be able to flash older Android 12 builds.
This is an unusual move on Google’s part, but the reason for the change is a new bootloader update that “increments the anti-roll back version.” Google has implemented this security measure in Android for several years now, generally to prevent exploits from older software versions from being implemented on devices.In any case, just know that upgrading to Android 13 on a Pixel 6 series device is effectively permanent
Here's the Android 13 Pixel update changelog