Thomas:
The report leans towards VR as the cause.
I suspect (given the circumstances, the main conclusion (above) and para 2.23) that what they actually mean is: Settling with Power and not Vortex Ring. [I re-iterate: VR is an aerodynamic state and SWP is an engine performance state].
Why don't you think it's VR? (yes, I agree that is an aerodynamic state). Over the years I've taught the recovery (at altitude) many times. While you often get some warning, a few times it's been like stepping off a roof - bam! pegging the VSI.
1,800 ft/min descent rate does not sound to me like an engine performance state. If you look at the torque over the last 30 seconds, it's consistently low: because he was flaring off his 100 knots of airspeed, I would think. So how did the flare, which should have kept the sink rate low, turn into such a high descent rate? VRS is certainly a plausible explanation in my mind.
As you mention in another article, there is a lot of confusion in the states as to the terms "Settling With Power" and "Power Settling". I've had people describe "Settling With Power" as a lack of engine power (that then caused the helicopter to sink into it's downwash and enter VRS!). So, you can certainly have a performance problem that gets you into the VRS envelope.
Not saying you're wrong by any means, just wondering why are you discounting VRS?
Paul