This is one (of many) areas in which Thunderbolt absolutely slays USB3: the ability to chain devices. Granted Thunderbolt anything is more expensive, but the performance is incredible.
MST (multi-stream transport) is a DisplayPort thing, which Windows uses. So you have DisplayPort over thunderbolt, and (presumably?) the multiple displays are opaque to thunderbolt. I've used this with thunderbolt/usb3 hubs that understand MST.
On Macs, however, they use thunderbolt's own ability to have multiple devices. You need to look carefully for hubs that support this instead.
Or at least this is my very limited understanding, born of utter bafflement with our work docking stations.
I post this mostly in order infuriate somebody with actual knowledge. Please set me straight.