I think It doesn't work how you say. I will explain you with a example:
With "open diff" try to lift a Wheel in the air, and if you accelerate only a bit the wheel in the air spin like crazy, the oposite doesn't recibe power and the vehicle doesn't move. The vehicle is stuck. This is correct.
But if you accelerate more, the wheel in the air spins, the oposite wheel recibes some power and the vehicle starts to move. This is imposible with "open diff".
I think "open diff" is really a "limited slip diff"
Am I wrong?
I've never had that happen in the game personally. If a wheel has been off the ground, it just spins.
Although depending on wheel weights, it's possible that increased wheel speed could move the suspension enough to cause momentary contact or reduce friction to grounded wheel causing some movement.