indeed but only LG must know what they are for
... How do you think they flash the initial firmware on the board?
Not really an idea, but I found an additional unused connector for a flat cable on the underside of the board, if you look closer onto it you'll see the connection from the assumed JTAG connector to that one.
however, I guess the flash the initial firmware via this connector. It not used and it's on the underside of the board, so you can easily access it just by removing the case of the NAS.
another pic from the underside