Back in the day, Southwest used to line up people in boarding groups. Within the groups it was first come, first served. People would line up sometimes an hour early to be in the first part of their group. Of course, being the first in “A” group was the most desirable since you virtually had your pick of the entire aircraft.
A couple of years after 9/11, the TSA began this “random” screening process. This was how “random” it was: the first person in group A, would be pulled aside when loading began and have their person and bags gone through. No one, especially a terrorist could possibly have figured out the pattern.
I vividly remember milling around at a Southwest gate, with groups B and C filled with 20 to 30 people. Group A would be totally vacant. As soon as some poor unknowing person took spot 1, suddenly 20 - 30 other Group A boarding pass holders would now rush into place.
After a year or so of this madness, I guess even the TSA figured out that there were pygmies in the darkest forest of Borneo that knew exactly what was going on.
If the accidentally published manual contains more ideas like that, the terrorist already know it all. And they are laughing.