I have spoken with two national banks so far. One with the POD accounts, and another with a very small non-POD account. In both cases the customer service person I was talking with was not the person making the decisions. Their job is to collect all the papers and fax them to whoever is making the decisions. They call it their legal department, but I doubt they got an attorney involved.
So the person making the decision is not available to talk with. The local customer service person receives instructions by telephone or email and tells me what they will or will not do. In the banks defense, dealing with estate issues is uncommon at local branch offices. The woman I was talking with said it had been about two years since the last time she had to deal with an estate issue.
It might be possible to go into a main office and escalate the issue to a higher level for a few of the accounts, but I also have to deal with some banks and organizations with no local presence.
Sending a bunch of possible beneficiaries in to ask if their names are on an account may be the answer. The banks will never notice the inconvenience. The people who have to go in and are told that they aren't beneficiaries will notice the inconvenience. It's a terrible solution, but without examples from similar situations it may be the only one available.