You are correct that seminar is often used for discussing research progress and looking for new approaches to research, but the term isn't universal. It can also mean a somewhat less formal course in which the students in the seminar present key elements related to the topic of the "seminar". I'll guess that he is using the term in this sense.

A seminar in the first sense would be peopled by those with very narrow interests and would usually have more than one professor and a few students. The professors might even outnumber the students. In the second sense of the term, there is probably one professor and the intent is to give students the "opportunity" to prepare and present topics so as to prepare them for a key factor of their future career.

I have been in seminars in the first sense a couple of times as a doctoral student but in the second sense only once, as an undergraduate.

Yes, it is good to follow the instructions of the professor. Your own research can be discussed separately with your advisor, who just happens to be the same person.

I'll note that the tag wiki for seminars focuses on the second idea, which is what you are seeing.

You are correct that seminar is often used for discussing research progress and looking for new approaches to research, but the term isn't universally used in that way. It can also mean a somewhat less formal course in which the students in the seminar present key elements related to the topic of the "seminar". The professor is there to evaluate and give feedback. I'll guess that he is using the term in this sense.

A seminar in the first sense would be peopled by those with very narrow interests and would usually have more than one professor and a few students. The professors might even outnumber the students and do much/most of the presentation and lead discussions. In the second sense of the term, there is probably one professor and the intent is to give students the "opportunity" to prepare and present topics so as to prepare them for a key factor of their future career.

I have been in seminars in the first sense a couple of times as a doctoral student but in the second sense only once, as an undergraduate.

Yes, it is good to follow the instructions of the professor. Your own research can be discussed separately with your advisor, who just happens to be the same person.