I have just begun to read this already enormous thread, so I do not know what others have posted.
My thinking is that they were purposefully obvious and threatening to see, without actually crossing the line and doing something illegal, AT WHAT POINT WOULD THE CREW AND/OR PASSENGERS INTERVENE?
They got their answer: NO AMOUNT OF SUSPICIOUS, 'THREATENING', OVERT BEHAVIOR ON THEIR PART GENERATED ANY INTERVENTION!
I agree. They were on a test run to see two things,,at what point would anyone take action, could they get the parts of a bomb on board. I do think they weren't doing a bomb at that point so if anyone had taken action, they would be innocent thus faking out security and weakening it. One of two incidents of faulty action and the security people will be seriously hampered by concerns of legal action, public outrage etc. These guys could have been enjoying a sadistic joke on the other hand.
Michellemalken.com is following and investigating this. Her site is excellent if anyone is interested.