Here's what I am seeing in my testing:
If I choose a product in the Product Listing Page - and click on Delete WITHOUT going to the media first - it does delete the listing (see screen shot Product for my selection for checking purpose on the other screen shots only )
Upon checking the resource library AFTER deleting the product - I see the product is there, and there is link is Null
(see screen shot Mapping)
Then if I try to delete the product pic within the resource library, even though it shows no mapping - it will not delete (see screen shot Deleting-pic)
Now if I go to the Media tab and select delete on the image, it does remove everything from the resource library. Then I have to return to the product listing grid and delete the product there.