Maybe he has minimal idea about med or 'why do you want to do med' but did umat anyway because of parents etc and got interview offers. No one knows. There are plenty of people like that. Obviously very unlikely to make it through when you are bsing your way.
EDIT: But OP, if you have no idea like just search up the internet. I finished my exams and had a couple of days to look online etc theres heaps of info. I mean if you don't really want to do med, the result of the interview shouldn't matter much to you, just don't come out feeling defeated etc so try have some understanding of why. Be honest (while selling yourself), not everyone has some dramatic story from their childhood etc. No shit everyone is very 'passionate' and wants to 'help people' and 'save the world'. It is a genuinely solid field and the research scope is incredible. Look at some of the Ted talk videos on new med research if you have time - some great results.