Much truth to this. I was working at Toyota when they were doing the tacoma frame recalls for rust through issues. The more often the owner had washed the truck in the winter, the more rust and holes the frames had. The best condition/solid frames were from owners who never washed it during the winter and parked outside. Seems counter intuitive but we saw the results first hand.2 things,
Heat is a catalyst and accelerates rust.
Water is required to for rust to work.
Park outside or at least in a cold unheated space.
Never add water. Wash is as infrequently as possible during winter.