[truth1ness]

Well for example, if I download the files or a zip from a browser it goes to my downloads folder. I can access that folder right from my dock as a 'stack' (every mac has it set up like this out of the box) so I can literally click on the stack and drag the file right from it to Calibre in two clicks (one click and a drag to be precise) from download to Calibre. Even if the File Explorer in Calibre is in the exact right place it takes a minimum of 5 clicks to get to the same point (also, the spotlight in the program finder only searches the local folder, not system wide spotlight, so you would still need to navigate to he right folder which is where you get into the 6+ click range).

Not to mention, if you manually go to the folder to do some initial clean up (if it's grouped with other stuff or has some junk txt files to get rid of, etc) then you have already navigated there once through Finder and if you can't drag it to Calibre then you have to go into Calibre and re-navigate there again a second time.

On top of that, Calibre allows you to drag a Zip file onto the icon, though the import seems to just get stuck. That makes even less sense that while zipped up you can drag it in, but when unzipped you can't, but if you grab the individual files in the folder then you can. The fact that dragging three different file types results in three completely different behaviors (one of which gets the program stuck) I think is reason to address this UI flow at some point. The flow you mentioned is clean and consistent: allow any of the three types to be dragged onto icon, if it is a folder or archive then show a dialog with folder/archive import options.