I would think the question is more of a bait question. I would ask this question to an applicant to bait them into responding back with a douchey or mindful answer. There's really only 2 ways to answer the question:
1) I've shadowed ----- specialist, so I've only had a brief glimpse of this speciality and I think it's very interesting. However, I know that things will certainly change once I go through dental school and I really find out what my strengths/interests are.
OR
2) I've shadowed ---- specialist, I know everything about this speciality. Even though I've never shadowed another specialist, nor have I even performed any procedure, I am 100% certain that I will specialize in ------.
Which answer makes the applicant sound more easier to work with? Remember, there is ALWAYS a reason for a question you're being asked on the interview. Sometimes, it's just for them to see you sweat.