Maybe I was not clear either.
somewhere, you might have :
a field that is already populated. Calibre will only overwrite, but never auto-clear. Fields can be populated upon adding from existing in BOOK metadata or from filename.
It is also possible (I don't use Goodreads) that BLANK identifiers are NOT considered an option on that PI. The data you see MUST belong to a specific identifier (GR and linked others), so it will be filled for the source that was used.
In a normal (using built-in sources) metadata search, a blank is a 'best guess' to the edition. (sometime it is way wrong
). Using an ID limits the results to that one (includes Not Found because that edition has fallen totally out of use.)
You can always add or remove identifiers at a later time