I imagine he has, but hypermedia already generally means hypertext documents. JSON with some URLs in it (which I think the article means - but I'm not sure) is something very different.

Yes sure I read it. But could not get what it means.

It means "Nobody understands REST and it has been so misused that it has lost its usefulness as a term, let's create a new term for the original concept, a term that better reflects what REST really means". That term is Hypermedia APIs.