They don't list all possible permutations of the endpoints when requesting "/", my guess is they only list the top 'root' endpoints that get you started so that you can then use the responses to dig deeper down the graphs.
As we know, one of the benefits of navigating the graphs using the URLs from the responses is that if the URL structure changes, end users will always know where to go.
Now what if you are writing a framework that wraps an API such as this. If you wanted to return data from deep in the graph, would you navigate the URL structure like an end user would and make multiple requests as you go or would you bake the URLs into the code and request them directly?
I know GitHub provides direct URLs to most (all?) child data but in my API this doesn't exist.