The people who you contacted don't understand any part of what the customer facing interface to their own job which is entirely usual. Its entirely possible that there was at one time instructions for return of the letter on an envelope that the party responding hasn't actually seen in years. They like a lot of people exist in a tiny silo with limited information outside of a tiny scope.
They kept asking you to essentially call a function on the actual public api and you kept on ignoring the error messages.
If you are tempted to feel smugly superior remember they were paid for their responses whereas you wasted your own time.
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