I have been building an app where I have the user select what apps they would like to track and then I display a device activity report of only those apps.
The device activity report shows data perfectly for the selected apps if the users apple account is "Adult". If the users apple account is "Parent/Guardian" or "Organizer" randomly the device activity report will show 0 minutes (no screen time data). Among randomly happening I have found a trigger for the bug to be opening any FamilyActivityPicker (even not the one used for filtering the device activity report extension) then going back to the device activity report extension on the profile page anywhere from 3-50 times. Once the bug happens repeating that process 1-2 times fixes it or removing screen time restrictions permission then adding it back.