I'm sorry, I didn't reply to Eddie's comments:
.. are you sure that that the helicopter was at full power to lift off?
No I am not sure at all but .. the Nr does (as TRC said) appear to be nearer to flight RPM.
When the resonance has put your blades out of symetrie it can be interested to lift off.
Yes it can but, if I remember correctly, the moment the vehicle is taken out of contact with the ground and suspended by the disk, the 'new' loading on the blades combined with the normal dynamic of centrifugal force eliminates the dissymmetry.
Pitch lift regardless off rotor rpm?
If he opted for chopping the throttle then, if it were me personally, I would probably introduce pitch (as a form of braking) until I could use the brake. But .. one needs to know what one is doing. Collective braking can introduce its own risks and one needs to be familiar with the sensitivities peculiar to each type in this area.
Has the pilot tried this or why is the helicopter turning before separating?
To me, there is very little videographic evidence to suggest that pitch was introduced. His 'turning' may well be due to the fact that he is starting to be bouned around in his seat. Conjecture I admit. The yaw does however saying something about the Nr.