I know you are just pointing out the dates.. but Cyberpunk 2013 did not release 1988 in Japanese. And I highly doubt Japanese cared about some obscure cyber punk tabletop from the states during that time. Especially one that painted Japan as the enemy.
Realistically in the western world, GITS only became generally known 1997 with the Movie and the fansub of it. So you can with some certainity say that both, Cyberpunk 2013 / 2020 and Ghost in the Shell, are unique concepts. In the sense that both were not aware of each other.