Imagine, for a moment, the car is stopped and you grab the door handle. The guy accelerates. Instinctively, when things we’re holding onto try to get away from us, we tighten our grip as a reflect, not a conscious decision.

Cop probably reflexively tightened his grip and then let go shortly after.

Not that literally any of that matters. It’s not like this was the ONLY charge this guy is getting and the sole reason he was arrested.