see the link of the german police from today
long story short: cause of the winterweather, on trucks standing the water/snow on the trailertop freeze and will fall off, while driving. Police checked truck-trailers on Ramstein-Autohof. 20 Trucks had to clean trailerroof before starting.
So - keep your distrance and drive safe pls.
It makes perfect sense to clear the car of snow. When I was living over there, I was told it is the law to clear the car of snow.
It sucked to be behind someone who didn't bother to clear the snow off of their car, and have it blow off their car in a huge chunk and land on my windshield, temporarily blinding me.
Regardless of being a law, or not, it is just common courtesy to not dump snow on others while driving.