A question for those with NOTAR experience - how good is the directional control at lowish power ie less than hover power?
If he was sitting in updraughting air - he was at the forward edge of the ridge - he may have found that he was struggling to keep the aircraft down when he landed - a combination of the surface and gusting updraught.
In those conditions, is the directional bucket capable of producing enough thrust, quickly, to cope with rapidly changing demands?
It seems that once he gets airborne, he should have been OK but if he was already struggling with yaw control, he might have been reluctant to apply full power pedal to arrest the yaw.