"Free DLC I don't own" filter not working as expected (also shows DLC I do own)

[qs-arno]

I've got this search filter that's supposed to match free DLC for games I own, that I haven't claimed yet. It does seem to be matching free DLC for games I own, but it's not acknowledging that I've already claimed them on Steam (the screenshot only shows one result, but there are a lot of them).

Is this a situation where the storefront (Steam) doesn't provide a way to report that I "own" these DLCs 'cause they're free, so there's no way for ITAD to put them in my collection? If so, would the "fix" be to just manually add each one to my ITAD collection and then just keep it updated whenever a new one comes out?

[qs-arno]

This may be related to #1630