Thanks for the write up. A qustion about the article:
Also, Play Services can read your SIM's country code if the SIM card is in the device. For example, Google will know a +49 (Germany) SIM card is inserted but will not know the full number. I am not sure about eSIMs. Play Services can also see how much global empty storage space there is on the device.
Are you sure about this? From what I recall sandboxed google services should have no access to any sim information. So are you sure?