The science of pilot/pax dynamics has three main constituents:
1) the vibration of the local area of the machine - its magnitude, direction and frequency. The vibration on meduim and large helicopters can vary markedly across the crew and passenger areas. If one could see the floor vibrating, it would look like a pond's surface in an earthquake, a series of peaks and valleys that stand almost defying gravity. If your seat is mounted at a peak or valley, it "sees" more vibration than if it is bolted to a place that is not moving (obviously).
2) The transmissibility of the seat, as measured at the human's position, that is, the seat's ability to quell or amplify the vibration. I have found seats that double the vibration, because they resonate at the frequency in question. Most manufacturers try to pick seats that reduce the vibration, usually by half. Sometimes, just more firmly bolting the seat, and tightening its joints can reduce the transmissibility measurably. The seat's response could actually make a lateral or longitudinal vibration translate into a vertical one, because the seat can rock or roll in response to a floor movement.
3) the posture of the seat - the verticality of the back, and also the layout of the controls, as they affect posture. A poor seat geometry causes the body to be held in an uncomfortable way, so that the extra vibratory motion makes the pilot work harder, and induce muscle fatigue as an extra component.
The study referenced in the lead post seems to leave all these important points out, and therefore it might be very simplistic.