[ontheotherhand]

Then simply look through all non-deleted documents and see which files are still referenced and which ones are orphans. Delete the orphans. Done.

[magicalist]

If the "working as intended" behavior is that these images won't be deleted since they can be linked to from elsewhere on the web, as appears to be the case (see my link to the old blog post above), they actually can't delete these old images.

[ontheotherhand]

"they actually can't delete these old images."

They can, it just would break those old links. A dumb decision ages ago doesn't force you to stick to it as you seem to imply.