This individual had T-cells that were: XX, XXY, and XY (mosaic Klinefelters), but otherwise genetically identical. They collected the XX and XY cells and coaxed them into being stem cells. Now researchers can use this stem cell line for research.
I see. So it was more about capturing the cells with the desired chromosomes and converting them to stem cells than about creating cells with the desired chromosomes. Thank you for your explanation!