I think you are correct in the issue here is the author is bad at interviewing and taking feedback. At the point where the interviewee didn't know the algorithm

I think you are correct in the issue here is the author is bad at interviewing and taking feedback. At the point where the interviewee didn't know the algorithm, he should have then moved on to another question and or ended the interview shortly after if that one answer was somehow the deal-breaker. The interviewer asked a question and the interviewee said he was not familiar. Interviewer proceeded to attempt to push him further.