Used on numerous occasions. Yes it does work, you transfer the inertia from the spinning wheel across the diff to the other side and it jogs you forward a fraction which can often be enough. Not everytime perhaps but I have got out of crossaxles as a result. If combined with a turn of the steering wheel as well, it is surprising what you can get out of.
It's a rudimentary version of the traction control using pulses of inertia rather than selective wheel braking.
The guy who broke a shaft must have brakes fitted from a different manufacturer because I've never known LR brakes to be that effective!
Myth? No way, try experimenting.
