I think the person interviewing in this article should have seen the person doing the interview was looking for short answers. It is not a perfect interview process but I am not shocked he did not get it as you can see his annoyance as the interview goes on.
He could have answered, "because Quicksort is N * lg(N)". Instead he opted to have a long answer about it depends how the algorithm is implemented. It either shows he is completely unfamiliar with big-O or he chose to give a annoyed answer. He could have also answered that there are a family of algorithms such as merge sort which are also N * lg(N).
A bit skeptical of the transcript as well. Knowing a MAC address in bytes off the top of your head? Almost every other person would first think okay how many HEX characters is it, and how many bytes in a HEX. But he has this knowledge immediately?