shortcut with filter "is not favorite" includes thousands of favorited photos in results

I would like to delete photos which have not been favourited from my iPhone Photos app. I have used the technique of selecting all favourite photos, hiding them, and deleting the rest, then unhiding favourite photos, but this becomes onerous with the amount of favourited photos. Hence inspired to create shortcut which collects and displays all the "not favourited" photos, to select and delete.

Unfortunately, the results from shortcut with the filter "is not favourite" includes thousands of favourited images!

Any ideas of what the problem might be?

Thanks!