If in page B there is already at least one link to page A and page A is mentioned more times in page B, page B will be shown both under Linked mentions and Unlinked mentions. This makes Unlinked mentions misleading and less useful.
It’s easier to show an example: in this example page A is “couscous”. Look at how all linked mentions show up in unlinked mentions just because the recipes repeat the word “couscous” several times:
+1
I would also like this functionality, both for Outgoing Links to ignore subsequent mentions and for an automatic way to “move” a link to the first mention in a note.