I had some Smart Matches for some people, let's call them John and Paul. Then I realized that John and Paul doesn't belong to the family so I removed them. The Smart Matches screen still showed results but with empty content.
Then I added some new people to the family, Clara and Esther.
Then if I open the Smart Matches screen the system shows that Clara and Esther are matches for John and Paul in the other family (where the original John and Paul matches were found.)