Well they have to be sure it isn't a terrorist plot to send ebola laced time bombs masked as bitcoin miners.
To an untrained eye these prismas may look like a suspicious contraption with all the chips on the outside and wires and stuff. All you need is a countdown LCD.
Then again, customs once held some of my SP10s which look like bona fide rack mount servers, so I can't pretend to know their logic. "Anything that doesn't have a fruit logo on it" perhaps. Never had issues with those.