I really think that this piece of documentation is obscure, and that you should add a few sentances to indicate that the help for specific format has to be called with that syntax.
The thing is not even in the manual (you have epub format, why not the bib format). Look for yourself:
https://manual.calibre-ebook.com/gen...b.html#catalog
This would save time to the user, and to you people in the forum.
But I see that you do not agree, and of course, at the end, it's up to you.