Remove Old/Nonexistent Images

We have asked that [1] be synchronized and this is working beautifully. However, it seems that the system is not removing old images, which have been removed from DockerHub. For example, we previously had the tag latest-gpu-py3-singularity, but this image was removed from DockerHub. I still see the folder in CVMFS, but of course not in DockerHub. Is it part of the system design that it will remove non-existent images or is this beyond its current capabilities? This would be a desirable feature. If it's not part of the plan, how else might we remove these old images?

[1] https://gitlab.cern.ch/unpacked/sync/-/blob/master/recipe.yaml#L62