I found something: "Mobile first, native ready
Designed and construed to be mobile-first, Flarum has strong requirements for its interface so that it works best on phones and tablets without sacrificing desktop users. "
Now I know why I find the site navigation sucks (IMO). I would strongly dispute the second part of that statement. Constant scrolling is not desktop-friendly. Pagination is. It explains the main page as well being boxes: phone users and fingers.