This is incorrect, no AMD chip (CPU or chipset) comes with thunderbolt built in. The x570 Phantom Gaming board uses an Intel Titan Ridge (see the obligatory AnandTech block diagram) controller hanging off of the chipset's PCIe lanes to provide thunderbolt 3. This is functionally equivalent to just buying a thunderbolt add-in card, other than the space requirements.
Ah my bad, you are right, I didn't meant to imply that it was actually provided by the x570 chipset, just through it as a part of the motherboard. I just worded it poorly.
https://images.anandtech.com/doci/14880/ASRock%20X570%20Phan...