I would say a whiteboard brief will demonstrate a better understanding of the topic that talking at an already prepared presentation and lead your friend into a better performance - if he really wants the job.
That's how I would see it if I was conducting the interview. Also, I would expect that the whiteboard technique would lend itself to elicting some good points from the student and would also be able to convey his knowledge of the subject when the inevitable tricky question comes up.
I suspect that in this instance, the organisation is looking for teaching skills and not lecturing skills.
Good luck (to yur friend).