currently it's not possible for anyone in the phone team to block migration of a RC buggy package version from amber-phone-staging to amber-phone. It would be great if that would be possible to do that to prevent breakage on the phones.
A likey simple way would be to assume a fixed location in gitlab like
and if the issue tracker there lists an issue with labels critical and suite i.e. amber-phone-staging or landing then the package must not migrate. This would also make PureOS converge to consistent repo locations (moving the phone forks over step by step).