So ... "if you're currently near someone who was previously diagnosed" ... the app is 100% useless then? Blatant lies. The app does not and cannot do what is claimed unless it gathers personal information. It knows exactly the time you ARE near or were near someone; that's the entire point of the app.
I assume that just means that resolved cases are removed from the database of positives… perhaps automatically for a rolling 14 days or something. Clearly you don’t want to be giving people an exposure alert for being close to someone who had it 4 months ago.