I may be wrong, but I believe the distinction is between if I were to link to your post with one of your generated images which would get served as og:image and

I may be wrong, but I believe the distinction is between if I were to link to your post with one of your generated images which would get served as og:image and if I were to re-host your image to have it stand in as an "open-graph image" on my site linking to your post then what are the repercussions for me.