I suppose we can iterate over the problems this would solve. It's not lost on me that we might want to reverse it into a positive assertion, as in code 418, but it might night to be split as in "I'm an air-conditioner", "I'm a heat pump", "I'm a refrigerator", "I'm a freezer", "I'm a cryogenic freezer", and further qualifications.
That said, is this truly a 4xx error? It seems to be a server problem, not a client problem, that the server is not a freezer.
Will revision 01 put more detail into §11 and §12?