The unowned cards tab in collection only displays cards the player owns 0 copies of
Steps to reproduce:
1. Navigate to your collection.
2. Switch to the Missing filter.
Actual Results: The Missing filter only shows cards of which you have 0 copies.
Expected Results: The Missing filter shows any cards of which you don't have a playset.
AdminWotC_Alan#83938 (Admin, Wizards of the Coast) shared this idea