Documenting requests' format and their return values is documentation and doesn't require an interactive site that looks totally real and makes you expect a real (rather than a dummy) answer. Which is not to say it's impossible, but it would be weird/unlikely. Usually when there is an example api request in documentation, it's a real (live) request, too, and this isn't even a documentation page.
looks like it is a demo of the API for people wanting to consume it. knowing what the payload looks like is not useless at all in this case.