The SCSI protocol driver on macOS is there mostly for USB devices speaking the enhanced storage protocol and similar use cases. That’s how a USB-SCSI adapter from 1999 actually still works on modern macOS.
The PCIe SCSI card driver on macOS is for LSI32032 and related cards, and at least as of last year’s release only works on an internal PCIe slot on a Mac Pro, not in a Thunderbolt-connected slot in an external PCIe enclosure. (Apple “just” needs to implement some extra functionality to support them in external slots, but they no doubt have lots of competing work to do.)
The PCIe SCSI card driver on macOS is for LSI32032 and related cards, and at least as of last year’s release only works on an internal PCIe slot on a Mac Pro, not in a Thunderbolt-connected slot in an external PCIe enclosure. (Apple “just” needs to implement some extra functionality to support them in external slots, but they no doubt have lots of competing work to do.)