Not... quite. Thunderbolt 3 did not carry USB 3.x over its bus, it's just PCIe and DP signals. All the Intel TB3 controller chips used in enclosures have a PCI

Not... quite. Thunderbolt 3 did not carry USB 3.x over its bus, it's just PCIe and DP signals. All the Intel TB3 controller chips used in enclosures have a PCIe switch and a USB root hub attached to that. This switch was ... not flawless ... to be diplomatic. It was utter shit, to be less politicaly correct. TB3 eGPUs famously struggled with their occassionally lagging and hiccuping USB ports so much so that the Visiontek Mini and the Razer 2 has two TB3 controllers to avoid this mess with the second TB3 controller solely providing the USB 3 root hub and almost all other eGPUs just gave up on them. USB 4 will carry 10gbps USB multiplexed with PCI Express and DisplayPort, native USB instead of hotplugged controller. Simpler.