I think the cover for that steelbook is the same print, the disc may be just produced locally in Korea.
There's no such thing as exclusive these day, they have abuse the use of this word in steelbook business. Maybe their definition of exclusive is different from us, to us "exclusive" meant no one else is having the cover release?
It might be exclusive in Japan to amazon but it doesn't mean other country can't have the same cover art. I have try to accept that this is the fact and that "exclusive" is just a marketing gimmick.
Anyway, just enjoy your purchase and buy it if you think you need them.