Halacha has standards for what’s reliable enough, e.g. two simanim/seals for meat. Is that 100% foolproof?
I don’t think that’s 100% foolproof, I think it’s reasonably foolproof and halachically sufficient, and there are many more such halachic standards that are the basis for Kashrus agencies’ policies.
The point that I'm trying to clarify is this:
As I understand it, when dealing with a frum owned establishment, where the owner has a חזקת כשרות, the role of the hashgocha is really to serve as a back up. מעיקר הדין one can be סומך on the נאמנות of the owner who is like any other עד אחד. It is for this reason that I don't fault the hashgochos in the Cleveland case or the Monsey case nearly as much as in this case.
Here we are dealing with people with zero נאמנות. As such, absent whatever halacha considers an עדות on the kashrus from an עד כשר the food must be considered non kosher.
Am I worng on these points?