I didn't even know Apple Maps has had this feature for some years. Just now I pulled out my iPhone 16PM and opened Maps, and there was a "Parked Car" marker accurately showing my car in the driveway outside the house, where I parked it last night. I don't remember ever seeing that before.
I wondered if the reference to dropping a parked car marker "when you disconnect your iPhone from your car’s Bluetooth or CarPlay system" meant you had to take an extra step to manually perform the disconnect each time you park, but it seems that when you walk far enough away from your car, this disconnects your iPhone from your car's Bluetooth, triggering the marker drop.