The point is not that all their ancestors were native to that particular spot in central Asia, but more that they were members of the central Asian ethnic group

The point is not that all their ancestors were native to that particular spot in central Asia, but more that they were members of the central Asian ethnic group rather than an ethnic group from further west, closer to the origins of agriculture and the technologies behind some of their material culture. So this is about the dissemination and transfer of technology between ethnic groups more than it's about geography. By native they mean central Asia, not the Tarim Basin.