There could be other factors. Anecdotally, I remember in the 90s my parents having an old and very box shaped Volvo. Driving through light snow one day my moth

There could be other factors. Anecdotally, I remember in the 90s my parents having an old and very box shaped Volvo. Driving through light snow one day my mother was struggling to clear the windscreen, we were on our way to pick up a hire car which ended up being a brand new Mercedes. The angle and shape of the windscreen was entirely different and the snow just followed the airflow up and over. That said, we have front registration plates in the UK which are probably less subject to aero improvements and ISTR the same phenomenon being observed there.