I haven't tested it exhaustively, I just noted that waking the car will start 12v charging, and checked it over an afternoons use. Scanning from the app will give the 12v voltage, so its quick and easy to do.
It seems to carry on charging for a period after re locking, but this may be the same time that the car takes to fall asleep normally - about 10-15 minutes or so
Unless someone has done a more objective test, it may be worth monitoring the 12v battery over longer times, to get an idea of how much it loses and then how long it charges.