For more points, try solving it in 25 minutes without running the code (i.e. as if it were on a whiteboard), and produce an answer that you're confident doesn't have any major errors, and be able to explain why it's logarithmic time. When you're done with all that, then run it and see if it passes. If not, you fail!

Demanding code that runs is silly, I agree. I think it can be valid to see how people cope.

I was once asked to produce the proof of the theorem of Pythagoras, which I hadn't thought about for many years. I failed to do it in the interview situation and later did it at home. However, I enjoyed the interview and I was also offered the job.