I'm not a big heli buff, (hope to be though eventually) but I notice the same sort of thing while playing Battlefield 1942, using Desert Combat version, flying the helis.
It's mostly noted when I'm coming in to do a landing, one wheel touches the ground while i have maybe a hair too much side moving going on, the wheel touches, and then flips the helicopter over on it's side on the ground.
Is this the same thing or is that just a bad landing? Usually I can make landings very good if I come in going straight forward. But taking off at an angle most of the time has it flip over.
We're just talking a game here too, and a game that isn't designed for helis or flight simulation with much in mind to begin with. But I guess the physics still make sense, having the disc not in perpendicular to the force of gravity and having a wheel/skid in contact giving a point for leverage and grip to throw the helicopter around.