I've been on some sites where the hamburger menu was atrocious and/or unhelpful.
When I encounter this, I will often just scroll to the bottom, where a lot of templates will put the "sitemap" stuff, usually with more descriptive text, so I can then find what I'm looking for.
It's not ideal, but people design mobile sites as if they're applying for a graphic designer job. Mobile design has become "smoosh it till it fits," and it just doesn't work well. It's a small screen, operated by a meatsack with a single giant thumb, who is probably driving 127 mph through a suburban neighborhood. It's a lot more than just "flow the three columns into one" kind of problem.
There's a link in the header to the nav element at the bottom. I think it works.
Yes, the necessary information is technically conveyed, but what's improved by this over headers or hamburgers? You'd be better off just having a fat header with all your links.
The blog post says users are conditioned. That's exactly the problem. The author hopes that users would be conditioned to find a site map at the bottom. I have the feeling 15-20 years ago in the ages of pure HTML that was more common. Nowadays 99% of the users don't learn that. It wouldn't be hard or impossible to learn. It's just that marketing driven design for fancy UI has ruined accessibility because those user have no voice.