The flaming drove me away, but i do need to (continually) correct one assumption people are making, which is the entire reason for the initial question.
Pwahlx is part right. The 9 hour delay was caused by the fact that he was picked at boarding gate and asked to return to deal with the box. By this he missed the flight, next was full, got on the third one 9 hours later.
The issue was never about the contents - he never "failed" any questions about contents. The customs guys made it weepingly clear that he was asked to return to checkin because it had not been checked in "properly". You can keep droning on about failing to stand up to the scrutiny / "investigation" about the boxes contents, but sadly these ideas are moot IN THIS CASE. It was made quite clear to him that it was solely about the fact it had gone down the "normal" baggage route.
And i quoted 2 personal examples, one involving myself, - that in our great desire to prove the validity of the terror threat and ignorance of contents line - we seem to be ignoring.
Driftdown seems to have hit upon the one "logical" explanation - that in form 45f of article 17j of the UK baggage guide, a BOX is viewed as cargo, and so has different treatment.
t1grm, that has been my experience elsewhere which is what prompted my initial question.
I am going to conduct an experiment. Every flight from now on I will attempt to check in a plain, sealed box-sized box. Will report back on the different treatment around the world. LOL.