> Compare the spec lengths: 681 pages for https://aomediacodec.github.io/av1-spec/av1-spec.pdf, 101 for https://www.iso.org/standard/77977.html.
And here we immediately see one important difference between them: the first link is to a 681-page PDF, which opens immediately in my browser. The second link is to a place where one can buy access to what it says is a 101-page PDF, after paying more money than it would cost to buy a basic laptop.