Yes many screeners have the capacity for critical thought but if your bosses override you and say do it this way it doesn't do much good does it? Some checkpoints are run strictly by the book and others allow for a little common sense wiggle room.
Me personally I tend to look at the rules in two perspectives, the letter and the spirit. Take the outer garment rule, it's possible to look at people from more than one perspective. While they have their back to me putting their stuff on the belt are there any unusual bulges? When they turn to face me is their clothing form fitting enough so that it can't hide anything or is the garment open wide enough so I can clearly see the contours of the person's body underneath the garment? Is the garment hanging oddly like one with something sown into the lining would be?
Observations like that are why i'm more liberal with what I allow people to wear through the metal detector but unfortunately if the supervisor overrides me and says they must come off then the matter is ended.