I think the argument is that the film was run at about half speed which would approximately make an object falling in earth gravity look like it was falling in lunar gravity. (Actually the film would need to be run at closer to 40% of its normal speed to make the gravity look right.) So the speed of the Rover would be more like 12 - 24 mph rather than the 30 -60 you mentioned. Without knowing more details about the flap it is only speculation to say it would behave any differently than it did if air is present and the speed of the Rover is twice (or 2.5 times) what was "advertised".