I don't think that Mp3tag is generating this score.
If you refer to this score
then it will be returned from the search server of the source itself: MusicBrainz.
This score will be builded with the given information.
What you can try is to use one of the "MusicBrainz expanded" scripts where you can search more specifically for ASIN, Barcode, Catalog Number or even directly by MB Album ID
