The git commit containing SystemUpdateManager says:
This CL adds system APIs in android.os.SystemUpdateManager. The APIs allow
system updater apps (RECOVERY permission required) to publish the pending
system update information, and allow other apps to query the info
accordingly (requiring RECOVERY or READ_SYSTEM_UPDATE_INFO permission).
Design doc in go/pi-ota-platform-api.
We don't have access to the pi-ota-platform-api, perhaps that could be shared with us so framework developers can understand how best to use this feature?