Found it. If the “Significant Locations” settings is disabled on the iPhone then the option “Show Parked Location” will not be visible in the settings.
If you go to Settings → Privacy → Locations Services → System Settings → Significant Locations and turn on “Significant Locations”then the “Show Parked Location” option will be visible in the Maps settings after you’ve connected to CarPlay/ vehicle’s Bluetooth system, you’ve turned off the car and have exited the vehicle.
That was it. I had it turned off. Didn’t want to leave any evidence the next time I wanted to rub someone off
Thanks. Good job finding that.