> This is the output of an app/templating system, i.e. not a single HTML page.

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.

> Have you ever read the HTML of any dynamically generated page? It's unreadable.

Not with that attidude... if you write consistently and with intention, it turns out just fine.

Check out the source for https://try.nodebb.org, for example. Dynamically generated, (mostly) syntactically correct, (mostly) human readable.

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.