Don't you screen all cargo ?
come on ! we all know how effective - and therefore infuriating - the present passenger screening is, and the bored operatives are in the public eye, just imagine how dedicated the boneheads would be in an almost deserted freight shed on a wet night !
There are sensible precautions in place now, but nothing is 100%.
This discussion is about how to deal with the odd hazardous cargo that does slip through, deliberately, or accidentally, placed on board, or other emergencies that migth benefit from another pair of hands or eyes, which at the end of the day might be the cheapest option ?