Yes, it allows you to view them, but they are not attached. The viewer is designed to shows all the contents of the currently selected folder - it has no idea that you just want to view an attachment. The attachment is extracted to your temporary folder and the viewer is invoked to display the picture. The viewer is a general purpose utility and allows you to view other images. Just as (for example) clicking a URL will open your Internet Browser to view a web site, but once opened, there is nothing to stop you viewing other web sites.