You're dividing between "real-world" and hypotheticality on shaky assumptions.
Yes, that file is in a repo with the substring 'mock'. No, that doesn't mean it doesn't correspond to a real-world problem, solution, or system.
Is this API real-world enough for you?
Sample Response (for once that token expires)
I hope it's clear that Elf's earlier example was not purely hypothetical. But that real-world products and services do need those sorts of things considered to help spread AS2 and other web/internet standards throughout the world outside of non-profits and indie-technologists.