One might ask what/why 21 people were either out of their seats or did not have their seat belts fastened only 20 minutes before landing. F/A's should have completed pre-landing cabin walk thru ensuring that pax were in fact in their seats and belted in. At that point in the descent profile the seat belt sign should have been on for at least 10 minutes. Something amiss (IMHO) given the high number of injuries at that particular point in the flight.
MS