This nice netherland answer should maybe from a non motorcycle person in the Yamaha Organisation with no experience with Travel Cases.
Even a moving from the cases is a construction detail, then it should be better the client will ask a Part Dealer like Hepco & Becker f.i. for help.
As Yamaha is a experiencend seller of Travel Enduros f.i. XT 1200 Super Tenere i never ever heard that the cases will move in the wind.
In my point of view this is dangerous and the sliding of the cases in the wind will de- concentrate the driver on top destaple the bike.
This is my personal experience with many Travel Enduros with case systems in 30 years.