If I quizzed engineers, what percentage of them do you think would get that exactly right? Prior to your post, I had myself thought — as Stanley seems to — think that Unix referred to the operating system by that name. I did not know that,
> By decree of The Open Group, the term "UNIX" refers more to a class of operating systems than to a specific implementation of an operating system; those operating systems which meet The Open Group's Single UNIX Specification should be able to bear the UNIX 98 or UNIX 03 trademarks today, after the operating system's vendor pays a substantial certification fee and annual trademark royalties to The Open Group.
But if I were exchanging information with a candidate, what Stanley provides is more than I would expect from a candidate (even from industry; he seems to be a student); that he isn't exactly on the mark should have been fine. If we really wanted exacts, the recruiter had ample opportunity to explain his/her position, but instead, we get nothing. Stanley took the time to both give his view on things, and give a simple layman's answer that conforms to that view when the tech jargon didn't seem to go over well. That he might be technically wrong is incredibly nitpicky, and I am not persuaded that that was the issue the recruiter had.
It still seems like an extremely weird qualification to require, doubly so again for an intern level position: you would still be likely to pass over extremely qualified candidates who just never touched a "UNIX".