This is the output of an app/templating system, i.e. not a single HTML page. Have you ever read the HTML of any dynamically generated page? It's unreadable.
All the HTML code in the app I maintain is pretty readable. At some point of complexity any HTML is difficult to parse, but if I hand-wrote a page in my app I think the HTML would be largely the same.
I don't think that's correct. The article is literally talking about how to write HTML, and explaining the benefits of writing it in this style.