They're talking about a PCIe card with a PCIe-to-PCIe switch chip from the likes of the ones available from PLX Technology (now Broadcom). In the absence of chipset and firmware level PCIe bifurcation support a PCIe switch is your only option.
https://en.wikipedia.org/wiki/PCI_Express#SWITCH
https://en.wikipedia.org/wiki/PLX_Technology
https://www.anandtech.com/show/13511/highpoint-releases-the-...