> An interview isn't an exam
That's not everyone's experience. Some interviewers do look for correctness, and an interview can be far more stressful than an exam, especially for people who are desperate for employment or just introverted.
The point is that whatever the whiteboard tests, it's definitely not someone's ability to sit on a computer and write good code all day.
It's more that a lot of companies are looking for much more than someone's ability to simply churn code out these days, and if this place was one of those then it simply sounds like this guy wasn't suitable for that role.
If, on the other hand, the company was actually looking for a coder to be able to write 100% perfect code on a whiteboard, and was planning on marking them down for syntax errors, then he's probably better finding out what sort of company they are during the interview than after accepting a job.