This is easier to explain with a screenshot, so in this example I have two drawers, one called "test" and the other "Test". Workbench only shows "Test", but dir shows both "Test" and "test":

You can see this behaviour quite easily using FTPMount and creating the two drawers or copying two files in and giving them names that only differ by case. It is not an FTPMount bug as I see exactly the same thing with the WebDAV handler I'm playing around with (in fact that FTP share in the screenshot is also a WebDAV share, so the data being looked at is identical with both filesystems)