In my experience as an interviewer, the original post was an example of what I always hope for--when the interview turns into a real discussion, and you're able to gain insight into the interviewee's character as well as his/her technical prowess. I always ask a mixture of open-ended and technical "quiz" questions.

More than that, I was a bit baffled by the negative responses. Willingness and ability to examine the assumptions behind a task are attributes I want in teammates.