It's not at all unfair. In fact I think that's a great example that while you need to be capable of getting good grades to study medicine and be a doctor, having stellar grades but interviewing badly isn't going to cut it. Doctors really need to have a strong mix of intelligence and also being personable and approachable. There is more to it than just academics and I actually find it quite encouraging that obviously they are happy to take someone who probably interviewed better despite not having the kind of 'top' grades people who apply to medicine usually have