first two photos are ground facilities. You don’t put rolling chairs on aircraft.
Ever flown on a commercial? Very smooth. Only need seatbelts in turbulence take offs and landings. The Chinese Y9 is a transport based bird like a commercial liner the flight is smooth. The crew don’t need seatbelts unless every thing goes wrong. Besides if it did get in to real trouble the operators in back bail out a door not an ejection seat. A complicated restraint would be more a problem than a solution.