There's a completely transactional reason for post-interview "thank you" notes, whether you're applying to college or for a job. It's to remind the person, who's probably interviewing a lot of applicants, of your existence and your qualifications. A good one includes a reminder of any parts where you think you shone. And if there's something you thought of later, it's okay to add that.

If their ego makes them take your thanks as sincere sucking up, fine. But you really do it for yourself, and the "thank you" is pro forma.

Of course this assumes you still want the position after having sat the interview. If not, feel free to ghost.