It's interesting that the way 'upload images' and 'upload single image' show up differently in the feed. I would expect to see the stars, shares and comments on both types, not just the group post. Also, they don't show up on the posts tab at all.
It's probably because the group posts has stars/etc for each image, as well as the post itself, where the single image only has them for the image.
It would still be nice in the case of a single image that the stars/etc for that one image would show up on the post in the feed.