[csense]

Any competent manager would agree with you; a candidate who knows they're not going to take the job, but comes in for an hours-long interview with several people anyway, is wasting your resources.

But that's not quite what happened here. As I understand the situation, the prospective employee thought he wanted the job when he went into the interview; but, during the interview he learned things about the place he'd be working in, and the people he'd be working with, that made him change his mind.

This is one of the main reasons that interviews are part of the hiring process: So the company and the individual can learn more about each other before a firm commitment is made, and cancel the impending hiring at minimal cost before it's final, if it becomes clear that that would be the better course.