How can a page on readthedocs NOT be on the list of content?

On Github - https://github.com/mozilla/DeepSpeech - there is a link to the documentation: https://deepspeech.readthedocs.io/en/r0.9/?badge=latest
But that page - with the title “Welcome to DeepSpeech’s documentation!” - is not on the list of content in the left column, so you can’t navigate back to it… How is that even possible on that system?