Is this a stunt or a useful descent technique? In many mtb movies about the style "Downhill" the riders casually twist their fork and front tire at jumps, such as here and here. 

Is this a stunt for "cool points" or does it aid in stability/speed in some way (as in, helps you finish first)?
Typically cool points, but it can be used to align the bike with the landing surface if the launch, trajectory and landing aren't in a straight line.