Same thing in MD. We sold a car to a dealer recently, and I returned the plates through a drop box on a Thursday. We did not get notification by email of the return by the next Tuesday, and called the insurer to cancel insurance. They retroactively cancelled it from the previous Friday. I’m not sure if they took our word or have a state database they can look at, but it was nice to drop the insurance on the sold vehicle.
I had a similar problem in Maryland a few months ago. Donated a car to some organization. Called insurance company the same day to cancel insurance on the car and took the plates to the DMV 3 days later. Got a letter saying that the car was uninsured and it costs me $150.
Make sure not to cancel insurance prior to turning the plates in to the DMV.
NY would charge you the daily rate for 3 days of very expensive insurance they provide if you let yours lapse in the same situation.
Same with MD. Had to send in my plates via certified mail to the RMV.