Can someone help me understand what DiskCopy 4.2 is actually doing in my scenario?

I have downloaded the System 2, MacPaint and MacWrite images from this site to my Mac SE with 6.0.8: http://www.earlymacintosh.org/disk_images.html

In DiskCopy 4.2, when clicking the "Load Image File" button it sees the MacPaint and MacWrite images and displays them in the list to select. I can write these to floppy perfectly. However, DiskCopy does not display the System 2 image in the list so I can't even select it write to floppy. Any ideas?