Most/all of these mods lie about the status of the trunk to trick the car into showing the open button when the trunk is already open so you can click the button again to close the trunk.
Can bus connection allows the control module to figure out when it should tell the truth about the status of the trunk.
If the car is in drive it will stop lying to the car. That way if you forget to close the trunk and start to drive off the car will beep at you.
If the driver's seat is empty, it stops lying to the car. There's no need for it to lie since there is no one in the car to press the button and this way if you are away from your car and want to check to see if the trunk is open or closed the Tesla app will report the correct status.