Beyond the moderate dubiousness of the intended mechanism here, if that thing isn’t somehow strapped down or secured beyond being nestled into the half rolled up window, that could very easily come ajar from significant braking or accelerating.

I can’t tell you how many times I’ve been in cars where the driver just piles loose shit all over their dash, or has a chandelier attached to their rearview mirror, which have come loose and hit people in the face or gotten wedged in some wonky position, and this has lead to an actual or near car accident.