Storing My Diesel Truck Over Winter Advice

Grit dog wrote:
Run DEF low unless you’re deleted. Run fuel low. Change the oil if you’re OCD and either disconnect or put a battery maintainer on it.

The full fuel tank thing is from times past when tanks had open vent systems and tanks were steel. And even at that, large amounts of condensation are really only a risk if exposed to the elements.
There will be a pile of people that say this is wrong, but I haven’t filled a tank in anything stored off season for 30 years. Carbed, efi, 2 smoke, 4 stroke or diesel.
Even old iron. I just spent 2 years restoring a truck. It did get started occasionally but sat for up to 6 months. Unheated shop, no problem. Only thing I did was put AV gas in the tanks so the fuel didn’t varnish.
All that said, only 6 months, you could turn it off, disconnect the batteries and shut the door and it would still be fine.

Okay, I'm a little confused. Where does the air come from that displaces the fuel as it's pumped out and used? Or does it create a vacuum? If the air isn't run through a drier, then it will have some water vapor in it, which can condense out and precipitate into the fuel.