The point is that an image of consequence, if real, would have a signed raw copy available which people could check to verify that there was in fact a real ima

The point is that an image of consequence, if real, would have a signed raw copy available which people could check to verify that there was in fact a real image that showed what a given edited image purported to show. If an image is being circulated but no one as been able to verify that a signed version exists, that image remains untrustworthy. This wouldn't stop people from editing images for aesthetic value.