This theme is not intended to be used as a normal theme. It is intended as a framework for creating minimal reproducible test cases. As such, one does not simply drop it in a site, but rather creates a repository specifically designed to isolate and demonstrate the issue one is facing.
The goal is to minimize the amount of ‘layout grunt work’ one has to do to create the test case.
That is also why it has no styling, except to improve the usability of the included debug tables and appease Google Search Console and Bing Webmaster Tools.