Are those truly x-ray machines? Not just magnetic coils? Seems overkill and I'd object to being exposed to ionizing radiation just for the purpose of validating my claim that I don't carry any electronic communication devices.
It's actually a pretty standard setup in China anyway... Pretty much anytime you go onto an inter-city bus / train or into a crowded space (museum / exhibition centre) you will go through a metal detector and your bag through an x-ray machine. So it makes sense that they'd just use the standard setup that the local security company would be used to.
