Upon re-reading the report: In Section 1 "Factual Information" on page 2 it indeed suggested that the collapsing seats under the occupants rendered the shoulder harnesses ineffective:
The Pilot and HLO were both incapacitated from injuries resulting from the combination of the rapid vertical deceleration and that both crewmembers were unrestrained by their shoulder harnesses due to the crew seats lowering as the seats deformed under the load.
However, further down a different analysis is presented. The stills from the video included in the report seem to show that (at least) the pilots body is already leaning far forward (due to the high centrifugal forces from the "excessive yaw manoeuvre") on or before 8 seconds after the take-off:
2.6: The shoulder harness has a locking mechanism that will lock the free play of the harness if the rate of acceleration is equal to or exceeds 1.5 g. If the acceleration is below 1.5 g, the shoulder harness is not locked allowing the body position of the crew to move forward. During the turn, the increasing rate of rotation was constant and approximately linear, up until the seven second mark.
...
The assumption is that for the Pilot to be inclined forward the rotational inertia has to be sufficient to propel the upper body position forward, all of which can only occur if the acceleration in the X-axis is equal to or less than 1.5 g.
This would not only have introduced considerable slag in the shoulder harness (allowing - together with the further 'play' added by the downwards collapsing seats - the pilots upper body upon impact to be first propelled forward onto the cyclic stick, and then out of the cockpit), but would also have caused...
3.3.2 Spatial disorientation resulting from the rapid onset of the yaw/high speed rotation combined with the effects of the rotational inertia forcing the Pilot and HLO forward.
Maybe these 'automatic' inertia reel seat belts are not that ideal after all?
In any case, one must assume that spatial disorientation would have rendered the pilot a mere passenger long before impact. And that the dumping of the collective (from second 7 or so) might not have been intentional. He may well have lowered the collective in the same movement that pushed his torso forward.
What I find remarkable is that the report doesn't mention what the 'pilot's story' is. After all, the crew survived and would in all generality be able to explain why the take-off was done without putting in anti-torque pedal, and why the pilot allowed the yaw rate to increase beyond (the possibly intended) 180 degrees pedal turn, seemingly without taking any corrective action. Is there is something about the UAE that I don't understand?