FWIW: Selecting the Proper Cover Helps Keep an RV Looking Nice
You already know what opinions are like. I'm not sure what "damage" they are referring to, but an RV being damaged by using a cover is counter-intuitive to the idea behind using one. I guess if it's a tattered cover letting the weather in, and then trapping water, and the freeze/thaw cycle wrecking the roof and components. Otherwise, a good cover should prevent such damage.
However, this is just my opinion.