Variety

Don't get me wrong. I'm not saying my answer is the correct or even the preferred one.

To go one step forward, the purpose of an interview question for secondary school children applying for admission to medical school is quite different from that you ask for a job interview. In general, in the latter scenario, the employer usually want to recruit just a few (often one) persons, and the aim of any question is to look for those with the suitable style and personality that fits the job and the organization as a whole. A specific type of answer is what they are looking for.

In contrast, admitting interview for potential medical students is quite different. The number of finally successful candidate is large, and, as I mentioned repeatedly in the past, it is not desirable to recruit people with just one type of personality - for example, in our example, we want some real scientist (to be, say, hepatologist) and some others with a convoluted mind (maybe as malicious nephrologist in the future).

Or, as what my friend NT told me, the admitting interview does not really aim to select students. All it does is excluding a small group of applicants with obvious psychiatric diseases - whom you would never be able to detect by looking at their examination result alone.