Hyper-G was a distributed hypermedia system developed at the Graz University of Technology in Austria, overshadowed by the World Wide Web and now long forgotten. See this PDF overview article: Hyper-G: A Large Universal Hypermedia System and Some Spin-Offs.
I believe it is because it can automatically (depending on the browser) start a download…
Thanks for the feedback, I edited the submission to move the link to the description.
I’d like to hear from @aperson@beehaw.org, but if you are right then it’s those browsers that are “not cool”, and linking a PDF is not the problem.
So would I - it does not seem like it would be too much of an issue, though I have seen people complaining about such things in the past…