The emphasis on God’s gift of land to the descendants of Israel is important because many Jewish readers of this book were living outside of Judea. Perhaps the author of Jubilees places the promise of land to the time of Noah in order to assure readers of God’s promise restore the people of Israel to the land in the future, or even to encourage a return to the land at the present time.The whole issue of the Land, of course, remains a major concern for modern Judaism.
Past posts in Phil Long's series on the Second Temple Period are noted here and links.