No sir, not a myth - an actual meteorological term. And you are wrong, fog is water vapor that is condensing because the air is oversaturated. I've never seen fog on a surface. Did you perhaps mean to say....dew?
There's frost and then there's hoarfrost. By definition hoarfrost goes from the vapor state to the solid state. It can be brushed off the surface. Think about two pieces of lead at room temperature. Put them together - no adhesion. Heat one to the melting point and then touch the solid piece and then cool to room temp - it adheres. Think of dry snow falling on a wing cold soaked at -20degC. Are you telling me that snow will adhere?
"While hoarfrost forms directly on objects as ice crystals,
rime forms when tiny, near-freezing water droplets, usually from thick fog and other clouds, attach to the surface of a below-freezing object and turn into ice immediately on contact."
https://www.accuweather.com/en/weath...hoarfrost/7092
Hoarfrost is described in many meteorological texts.
Frost - AMS Glossary for an easy one.
Regardless, even if that frost did adhere to the wing like window frost, it would not affect the airflow. It's thin enough to see through it, it's on the aft portion of the wing, and it's far smoother than the screw heads, access panels, and other structure on the wing. But we continue to waste money and the environment on spraying clean wings because every uneducated idiot like this guy has a phone camera and the FSDO on speed dial.
Not sure why the "former bush pilot" comment was made. Dogma? Ok let's go - four years conducting aviation weather research including aircraft icing for a government lab funded by the FAA and years designing jets for Boeing as an aerospace engineer. Oh yea and I flew a 1941 warbird with a 65hp engine, no GPS, no electrical above the arctic circle - in the bush. Oh and I've flown a CRJ200 (supercritical wing) with the typical outer 4 wing panels having hoarfrost on them. If you want to pull out resumes and compare who's bigger, I'm game. But I'd rather argue physics. Crack a book sometime.