Okay… update as to what the script does. See here: Picard Artwork Choices - how does it choose a cover? - #8 by IvanDobsky (warning… loonatic hyper thread… 
Just the two posts #8,#9 are relevant)
Basically… a release like this: Release “Tonite Let’s All Make Love in London... Plus” by Various Artists - Cover Art - MusicBrainz has got the first part of the booklet tagged as “front, booklet”. That made a mess when I downloaded as it was named “Front.jpg” and I wanted it to be “Booklet.jpg”
So script fixes the times when a booklet is also tagged as Front.
It has a narrow use case of making sure a booklet is really named as a booklet with all of its parts.