The flag allows overriding the value of config_tether_upstream_automatic on released R devices, as issues have been found on devices where an overlay was used to set it to false. The flag is only usable on R devices, as S devices can either not set the setting to false, or fix the underlying issues. Bug: 173068192 Test: atest TetheringCoverageTests Change-Id: Id99638916e08e596fab21cedd7bfe39906ce2fe5