"I don't buy this for a second. Think about it"
It deserves more than one second to thinks about it.
Your speculating that the vacuum would be less than pretty darned high, I'm speculating that it could be an issue even if it is less than pretty darned high, which it might not be. We need to know that before we say it's silly.
True dust is heavier than air but if you tow a trailer down a dusty road at 100km/h for an hour you'll see dust in the mirror cause of the turbulence, and there will be dust in nooks and crannies all over, I wouldn't hazard a guess about the vacuum level.
Just something I've heard of and do, could be crap for all l know, but only takes a few seconds to do, and no harm in doing.
I also put an oily rag in if in storage for a while to stop condensation and critters.