Don't you think an interview is a collaborative effort? What signal is the interviewer getting from a candidate if they're asking about work experiences and the candidate is answering with personal non-professional anecdotes?

Assuming that the candidate was in the wrong here, and the interviewer wanted work anecdotes, why didn't the interviewer guide them to the right topics? If they didn't guide them to the right topic, your assumption that they wanted work examples may be flawed.