+ AA6YQ comments below
Oops, sorry about that. I didn't quite have a good understanding of how the Unconfirmed filter worked.
I now see that my needed filter window does populate with an unconfirmed entity. Provided that the new station call sign is different from one I have already worked on a given band/mode.
+ Correct. SpotCollector doesn't consider a station to be "needed" if you've already worked it in the needed entity, on needed entity-band or in the needed entity-mode.