I think that's exactly right in the typical case. However, if the company is dealing with a recruitment agency it might be useful for the company to let the ag

I think that's exactly right in the typical case. However, if the company is dealing with a recruitment agency it might be useful for the company to let the agency know why a candidate was not suitable, so that they get better candidates in future, and the recruitment agent (who is a "double agent" really) might pass the information on to the candidate (probably not in writing). I've heard of that happening. Also, in cases where there isn't a position to be filled, but the interviewee is trying to persuade the company to create the position, in those cases the company can be a bit more open in saying why they have decided not to proceed. I've heard of that happening, too.