GrapheneOS
Great many thanks for explaining about adb.
When I run a SeedVault backup about 40% of my apps are reported as "apps that do not allow data backup". Seedvault has open issues Initial support for backup of D2D-only apps and Pretend to be a device to device transfer - fake-d2d. These observations suggest that the backup system is not currently using device-to-device backups. Or have I misunderstood again?