Offering clarification is never necessary, but I think that clarifying what the vast majority of us consider older fantasy will help people better categorize books, which can only help.

The important thing is to do it courteously, and since thnidu phrased the comment in a good-natured way, I see no problem with it.

Or did you mean my reply? In that case, you're right, I have added nothing useful to the conversation, which does make it kind of unnecessary. If it's annoying, I can certainly delete it.