You are absolutely correct. There aren't enough books in the world to tell someone how to deal with every possible situation with people. Where the SOP comes into play is with routine passenger/TSA interactions. Where the deviations come into play it requires common sense and a bit of knowledge to ascertain what the passenger is saying is accurate and that a hand screening accomplishes what TSA is tasked to do (keeping weapons, explosives and incendiary devices off of the aircraft).