When the website is full screen on a desktop, clicking on the left menus will never open that root page. For example, clicking on Extras should take you to https://vsoch.github.io/mkdocs-jekyll/docs/extras/ except it will only ever change the domain to https://vsoch.github.io/mkdocs-jekyll/#pancakes-extras
It is only once you make the window small enough to be a mobile site and navigating to extras through the hamburger menu will that then open the root page of extras.