I once heard something along those lines. Last night upon leaving work I got to my car to find that the windows were - opaque with frost. I had to sit with the engine running and the heat on full for around ten minutes before I could safely drive the car.
The car hadn’t had a wash in a while, so today I cleaned it. I’m wondering how ‘frosty’ it’s going to be tonight (because it sure is one helluva cold night tonight)
Dirt on the windows gives a place for water to collect as the temperature drops, so when it drops below freezing there is more water on the glass to freeze.