> Why on earth would you want to load JS before content is loaded but not after?

apparently, single-page-apps is an unstoppable trend. I tried to disable JS and 99% site won't work.

But for content sites, after the article is loaded, disabling JS provides a much better reading experience.

> but no one would choose that over the usability of Google Maps or OpenStreetMaps today

That's a valid use for JS. But if you think about it, can we make a js free map tool using technics from OP's article? https://codepen.io/rebane2001/details/OPVQXMv