waterlubber There is a significant difference in privacy between coarse tower-level data and fine GNSS data.
Agreed.
waterlubber Allowing the latter is a serious omission, especially given gOS assumption of the carrier as a hostile party and the fact that, given the insecurity in protocols themselves, this would effectively expose precise location data to an extremely large number of people.
It's one thing to dislike fine-grained location tracking. I think it's quite another thing to describe the situation as "a serious omission" when the project has clearly stated: "Airplane mode is the only way to avoid the cellular network tracking your device and works correctly on the devices we support."
waterlubber "Simply use your phone in Airplane Mode all the time" is not really a suitable option for a cell phone operating system.
GrapheneOS reportedly works quite well on the Pixel Tablet, which does not have a cellular modem, and some posters on this forum have indicated that they purchased a Tablet for this reason.
People who choose to purchase a cellular phone and turn on the cellular modem are choosing the benefits of having a cellular device along with the costs. We might all wish for those costs to be lower, and perhaps over time they will be. But I think that representing the situation as "a serious omission" on the part of the GrapheneOS project seems unwarranted.