Vid would only be credible if they had used an air flow meter to measure the difference. The amount the hinge flap moves is dependent on it's weight and the air flow and neither is known - easy to make the difference look much more dramatic than it really is.
Even if the air flow is reduced a bit, just turn your fan up a notch. I don't think there's a need to run the fan at the 100% setting very often plus they're quite noisy at the higher settings anyway. We don't often run ours above the min. setting and the Maxxair II cover works great.