And if you're wondering why this behavior is not a user option, it's because of liability.
Car puts itself into park at 3 MPH when the driver doesn't have a seatbelt on? Minor annoyance for the driver.
Car doesn't put itself into park when you get out and it rolls into the street and kills someone? Major lawsuit for the Manufacturer. It's happened already with Mercedes and their sprinters.
From a human factors standpoint, it also needs to work this way on a Tesla. Without the whole start the engine, put it in gear, put it in park, stop the engine routine, Tesla was able to make the car just work with the only action being putting it in drive, which can be pretty magical. When done, you can just undo the seatbelt, open the door, and get out. As long as any of your cars allow the auto park behavior, having some of your cars do this and some not is just really bad design. A driver could be used to the auto park behavior and then drive a car that has this turned off and the car would creep away as they get out. You need consistency in behavior in your products, especially around automation like this.