UKHeliBob:
Pressing 2 buttons at the same time sounds to me more complicated to operate that pressing one button with a single purpose.
Totally. And given it has to have the built in delay (not a delay() delay 
, but a lag let's call it) to see if the second button is still going to be pressed, there will ALWAYS be the chance of a false change up or down if the operator's a split second late on the second button, like a finger slips and misses the press. Also going to neutral quickly, with an unambiguous operation, may well be an added safety feature, to disengage in an emergency.