I can only assume you were flying a jet and I doubt a high powered jet flying above Mach 1 would not act quite the same way as a low powered biplane flying along at about 100 mph.
I suspect the low powered biplane would be far more susceptible to any turbulence than your modern jet, and that is all AnKor is attempting to simulate.
Plus a modern jet has a far more sophisticate seatbelt system holding you rigidly in place versus a simple lapbelt in the WW1 planes which allows you to move your upper body around due to banking or turbulance.
You missed the part where I mentioned I had just flown an aerobatic taildragger. The Citabria maxes out at 1650lbs, I was flying at 1400lbs. Whilst it has a shoulder harness to go with an ordinary seatbelt, the shoulder harness is not an inertial reel type. So it has the same jostling of your body as a WWI airplane. I cruise around in it at 110 mph and it is extremely susceptible to turbulence. Taildraggers are all I fly now, and I average about 12 hours a month.
FWIW modern fighter restraint systems allow for considerable movement, the seatbelt is the primary restraint except for ejection sequence when your upper body is restrained firmly (rigidly to use your term) against the seat back as you ride up the rail. In the Phantom I could turn my torso 90 degrees in the seat by leaning forward just a bit, the Viper didn't require that much twisting but one could grab the towel rack on the opposite canopy rail (L hand on R towel rack and vice versa) to crank your torso. Basically any maneuvering you can do in the driver's seat of your car a fighter pilot can do in the cockpit whilst strapped in. HTH
But again...if you guys are groovin' on AnKor's mod, more power to ya. Honest