I know he knows how to do the coding tasks; he knows I know it; he put
up a site that challenged everything we think about academia."
Since the goal of the quiz was for the students to demonstrate "they
know how to code" and "I know he knows how to do the coding tasks; he
knows I it..." I don't believe you have a problem. The student has
persuaded you he knows what you wanted him to know. PLUS, he
challenged everything. What more could a teacher ask?
It seems to me the Internet is about links and finding them. Your
quiz and the issue is linking and the coding that makes it possible,
not what is at the end of those links. Had he simply linked to a site
that told how to link I think that would be cheating.
But he not only knows the stuff, he was able to apply it in a way that
has you and your students thinking. I'd give him an "A" for
challenging the academy.