You did see the part I mentioned about converting a book After a 'generated cover' had been made.
Also, the are now many generations of Generated covers in my collection. With some, the Calibre version number was what changed. There has also been a few 'style' revisions in the last year
We need a Optical Image comparator to examine the 'cover' image for certain Calibre cover image 'key points' (sort of what a '$ bill changer' does ) matches.