I fail to see the problem. Frankly you could juggle flick knives or swords in the cabin if you wish
I think the point is that nothing sharp with a length of over 6 cm should go on a plane, (or nothing sharp at all according to the TSA mongs). Sharp objects could be used to force aircraft crew to the possessors will.
Onetrack - I'm glad that I didn't live in OZ when I and my mates experimented with making bombs in our teens.