I don't think it's incredibly unusual. On sensitive machines in corporate settings you commonly disable pretty much everything on every page that isn't in the 'trusted zone' or whatever.

Personally, by default I shut down all the browser crap that might needlessly allocate RAM or allow memory leaks or slurp cycles without giving me some kind of value. I think this allows me to hold at least a few hundred extra tabs open. For technical documentation I expect text, hypertext and static images, if you're going to require JS and WebGL and whatnot I'm going to assume you aren't entirely honest with me about the information we're about to share and I'll probably sandbox a scrape of the documentation if I really need it.