This is true for remote images, but in particular for local cover art.
Changes only in cover art without a "Show more details" button are confusing
No stable sort order for cover art saved to ID3
Only save files if they were changed
Perfect files shown as needing saving
Changes to certain tags and cover art type don't appear to save
Some previously tagged & saved Albums always show as updated despite no tags changing
Images tagged with extra types that the user has chosen to ignore should not be shown as 'modified'