As you say these agencies are set targets to get people off certain benefits with no real regard for personal circumstances - it's entirely a tick box exercise.
More worrying is the huge percentage of cases that go to appeal and then get overturned, how much are those months of investigations and panels employed at tribunals costing?
All that presupposes the person has the stamina to live through the long battle, by which time as you say they may well be out on the street.