Your slides illustrate a custom response payload which happens to use codes that numerically match HTTP status codes. You also use a response message, I think we actually agree. I'd recommend using a different numerical namespace to avoid any possible confusion about the semantics of those codes. Just because they sound the same to one person reading the spec doesn't mean they will make sense to others.

Understood on that point. The response codes are in those payloads purely for illustrative purposes.