All 'Flight Mode' means is that the radio in the device is switched off. All the PDA functions, including digital camera if fitted, remain on.
It's not a low-power radio mode or anything like that -- it means radio OFF so the cellphone functionality is completely off. There's nothing for the CAA to test, so I don't believe that reason for a moment.
Devices like BlackBerry actually call it Radio off/on -- which assumes a degree of intellect on the part of the user, of course.
