Too Long; Didn't Read
Whiteboard interviewing is not a good way to judge the ability of honest applicants. Interviewers are usually untrained and out of their depth, repeating how they were interviewed (badly) Sometimes they enjoy the discomfiture of their candidate. The interviewer’s lack of skill creates its own tension; maybe he has an impenetrable accent and the candidate has to ask him to repeat, maybe several times. Maybe he sniffs and fidgets and offers misleading suggestions when the candidate is expected to concentrate and show his best work? This is unreasonable. The interviewer is behind on his own work already (that's likely why they're hiring)