Self Selectors are worse. People with something to hide are much more likely to self select.
Doubtful. I would say that people with something to hide are much more likely to avoid doing anything that might bring additional scrutiny if they are noticed.
Also, the couple / three times I've seen TSA pull random people into the pre-check line, they have done the explosives test on all their hands.
I have seen countless random inclusions during lineup, and I cannot recall ever seeing any of those people get more screening than me. I can count on one hand the number of times I've had the explosive swab this year.
In any case this was jumping the line after document check which is worse still.
Again, from a security standpoint - why? Their documents were verified just like yours. When they go through the checkpoint they get the same security screening you get. Are you saying the screening you get is inadequate?