If there's an ISBN, it shows a link in the Ids field. I personally find this a bit of a bad metric as a) I have many non-Kobo books with ISBNs and b)
not every Kobo book has an ISBN see edit.
I was specifically referring to the download metadata search dialog in this case. I suspect it's the ISBN thing again.
EDIT: Interesting:
https://www.goodreads.com/topic/show...3--isbn-prefix