It seems there's likely a new US safety standard due to the reasons stated above in the quoted post about accidental deaths involving non-conventional automatic shifter controls. I think these new cars if they are stopped, just go into park automatically. My Honda does that and so does my Genesis. The workaround for moving the vehicle with the door open is usually having the seat belt buckled and then it will let you put it in drive with the door open. If I'm trying to look down with the door open to get a better look with regards to parking etc and to slowly creep up with the door open, I have to have my seat belt buckled. I'm assuming it's going to be the same in the automatic mustangs.I was familiar with several deaths involving Jeeps, Ram Trucks, gear shift knobs, vehicles coming out of gear, people getting run over, etc. I later found a recall from Hyundai involving wiring.
I then googled, "vehicle safety cannot move when door open", and found several models and years highlighting this safety/nanny feature, especially on vehicles equipped with e-brakes.
I suspect it will become common and standard to all models everywhere. Similar to what happened with Toyotas and stuck throttles or failing throttle position sensors. Programming was changed industry-wide to ensure when someone mashes the brake pedal, everything else is overridden and the car stops.