If my chemistry serves me correct. Oil/oil based products and rubber do not mix well at all. The oil will deteriorate (eat away) the rubber.
There are a lot of suspension components with rubber based bushings, engine mounts and fuel/break lines with rubber seals. Rustproofing chemicals are typically oil based with chemical adhesives and if they are improperly applied - get sprayed onto parts with rubber, you'll have more to worry about then rust.
I'm speaking from experience... I had to replace all my suspension bushings and main drive shaft guibo

THEN!! when the engine mounts disintegrated (they are rubber based), the whole friggin engine started to move when the breaks where applied!! That was a nightmare to replace... scary to see your engine being slightly pulled out so they can squeeze new mounts in.
Oh, and as for the doors, if they spray that crap inside the doors, and destroy the sheeting action that occurs - the doors are designed to funnel/sheet water down the inside door and vent it through small water drains at the bottom of the door jams. If they get plugged, water doesn't drain and builds up causing moisture and condensation and rust. Worst is the accumulation of water in the door jam and then it freezes over night (remember what happens to water when it freezes - expands.)
Also, in my case, the undercarriage was sprayed with a tar based sticky substance, and it was applied over the cooling fins of the transmission housing and rear differential (that had cooling fins as well). Now, the transmission and differential weren't properly dissipating heat causing shifting problems and overheating the diff. What a nightmare to get that tar removed. NEVER AGAIN!!
I'm telling you it's a mechanics dreams and an owners nightmare.
My rule of thumb. If it's a car you really like, don't drive it in the winter, and buy a winter-beater.