Downloading / Editing Metadata
in the Library (view) mainly affects the DB (entry).
It will also cause metadata.opf ( a backup of the data) to update in the Titles folder. Same goes for cover changes.
IF... you change either the Title or Author, the book moves to a new location within the file system.
If that is all you do. The actual book files do not change INTERNALLY. The file name may change if you change the TITLE
It takes extra action to force a Library copy to update internally.
OTOH if you SEND... (again) those get updated on the fly
free file sync only sends updated files to your backup target, and it is fairly quick if you have bandwidth.