Is this new that 1K/Star Gold can not reserve anything but a center seat
There is no Star alliance gold seating benefit (though airlines may choose to provide their own elites with better seating like UA *G having preferred/E+ access on UA, or even extend to other airline's elite).
in this case, ANA does not offer any benefit for seat selection- *G does not give you anything extra over a non gold passenger (holding the same discount economy ticket).