I have a Honda top box fitted to the bike and I removed the top box to clean the area underneath it.
The plastic plate that the top box connects to moves approx 5mm from side to side.
The plate does not just move from side to side but is 'springy' like it is supposed to be like it.
There is no back and forward movement.
I have removed the 4 x fixings and it would appear that the only way to remove this sideways play would be to install some thicker washers.
I do know that Triumph build in movement to their panniers allowing them to move and is this a similar thing?