Sorry, I think I did not read well the background info.
If one wanted to follow the manual command line instructions in order to have Android 13 (T), then one would first need to revert the phone to OxygenOS (12) in order to fulfill
Before following these instructions please ensure that the device is on the latest Android 12 firmware.
It is the OxygenOS (12) which will contain the required Android 12 firmware.
Bear in mind