Yep, i did that course. For river crossings thats what they recommended. Windows down and seat belts off.
The logic behind that is that electric windows may fail if they get wet, and if the currents strong you may not be able to open the door, trapping you in the vehicle. So windows down.
Other side of the story is that with the windows up you are semi sealed in the vehicle increasing your chances of getting to a point where you can exit the vehicle safely, rather than it immediatly filling with water.
Seat belts are the same, NZQA course says seat belt off for a rapid escape.
Other side is seat belt on to hold you in place should you get rolled in the current, prevents knocking your self out and drowning, you take your belt of when you are ready and exit the vehicle.
With the windows up, you could/should have plenty of time to get your belt of when the time is right.
Leave it to personal preference.
There was lots of stuff on that NZQA course that was not very practical IMHO. Work was payin, so i didn't complain about two days off in Greymouth driving noname road in a work Hilux
