Because it reflects how the writers solve problems. They needed a website. Did they spin up a docker container of wordpress, install a theme and some plugins until it looked the way they wanted, and write content in an in-browser WYSIWYG editor? Or did they write their content as HTML, and copy it to a server running HTTPD? Those two solutions represent different values, different philosophies, about how to use computers. It is good to see that the author's website-building approach is consistent with their operating-system-building approach. It lends credibility to the sincerity of the project.
No, it primarily reflects the problems. For example, the Gentoo and Arch Linux run MediaWiki. Does this tell you something about their "values or philosophies about how to use computers"? No, a static site generator would simply not be practical for either project. What renders documentation HTML in the background tells nothing about either project's approach to operating system development.
