As DaveReidUK suggests, those (unrestrained) towards the rear of the aircraft are more likely to be thrown about due to the longer levering arm towards the rear of the aircraft. A similar incident occurred with Qantas around 5 years ago - this is an extract from the ATSB report...
In-flight upset involving Boeing 747-438, VH-OJU, 110 km SE of Hong Kong Airport, on 7 April 2017
Contributing factors
- After overwriting the hold speed in the flight monitoring computer , the flight crew did not identify the need to re-evaluate the hold speed for the higher than expected hold level.
- Prior to entering the hold, the aircraft’s speed reduced below both the selected and minimum manoeuvring speeds. The crew did not identify that the aircraft was operating below these speeds.
- The reduced speed coincided with the turn to enter the holding pattern and the level capture. These factors resulted in pre-aerodynamic stall buffeting and probable stick shaker activation.
- The pilot flying attempted to arrest the rate of descent prior to completing the approach to stall actions. The pilot monitoring did not identify and call out the incomplete approach to stall recovery actions. These combined actions led to pilot induced oscillations and further stick shaker activations.
- The operator provided flight crew with limited training and guidance in stall prevention and recovery techniques at high altitudes or with engine power above idle. (Safety issue)
- The passenger in seat 63C was not wearing a seatbelt at the time of the stick shaker activations.
VH-MLE