But this is precisely the lack of clarity I think TSA is going for here. Someone who plans on hijacking an airplane will be more successful if they can game the security system. If there is inherent unpredictability to security, i.e. "snake the guardrails all willy-nilly to put people in certain places and then randomly pull some out to go through a different version of security" it becomes more difficult plan for in advance. Personally, I have absolutely no problem with the unpredictability of TSA, I just wish they'd leave the Pre Check lanes alone. The reason I do Pre to begin with is that I can avoid the mobs of infrequent travelers who are still trying to figure out that they need to collapse their strollers, take out their liquids, remove their computers, take off their belts and shoes, etc., etc., etc. If you want to experiment, don't do it by slowing down the lane set aside for frequent travelers who have been vetted and are more efficient and the whole security process!