I value negative space in the same way that my dream is not to pile my plate with as much as I can at a buffet.
And yes it works on a phone as you can easily zoom in, but inclusion of responsive design, e.g. moving the sidebar to a footer, and use larger fonts would significantly improve legibility and usability. This is not incompatible with a simple and fast-loading site.
The site leaves a lot to be desired, but it loads fast.
I think he sold printed dead-tree manuals.
Now PDFs are bundled:
Someone mentioned an "in between" option and that's where I personally tend to land as well. A lot of modern websites are so media and JavaScript heavy that they take a long time to load, have many layout shifts and feel sluggish when you use and navigate them. That is not good user experience.
On the flip side, I think there is a lot to say for "responsiveness", font choices and media that helps the user experience. I am a minimalist, but legibility of copy and making intelligent layout decisions relative to the viewport size are "modern" techniques that can greatly aid UX when understood and applied properly.