DjBeau I tried creating a Google account without phone number by making a new user through GOS. It works, but there's no other way to do it. So I'm wondering if it's working because google is simply grabbing the number from the SIM card?
On GrapheneOS that would require Play having been granted the Phone permission.
Google's account-creation system uses a variety of heuristics. If an account is created using a residential IP address, for example, a phone number might not be required.