Not quite: https://twitter.com/whitequark/status/1097777102563074048

"Thunderbolt, uh, does not expose PCIe lanes directly. Thunderbolt is an MPLS-like packet switching network that can encapsulate PCIe TLPs over a PHY and MAC without a spec, chips without documentation, and software with barely any support."

Thunderbolt encapsulates PCIe frames. It's not PCIe any more than say ethernet is UDP.