Not for the past decade; it's been no connectors for most products, but standard PCIe connectors for the Mac Pro, and NVMe over Thunderbolt works fine.
>> XHCI
> Not on Lightning.
Again, not relevant to any recent products. And I'm pretty sure you're misunderstanding what XHCI is if you think anything with a Lightning connector is relevant here (XHCI is not USB 3.0). You can connect a Thunderbolt dock that includes an XHCI USB host controller and it works out of the box with no further driver or software support. I assume you can do the same with a USB controller card in a Mac Pro.
>> AHCI
> How exactly would Apple not support AHCI?
This might be another case of you not understanding what you're talking about and are lost in an entirely different layer of the protocol stack. Not supporting AHCI would be easy, since they're no longer selling any products that use SATA, and PCIe SSDs that use AHCI instead of NVMe died out a decade ago. But as far as I know, a SATA controller card at the far end of a Thunderbolt link or in a Mac Pro PCIe slot should still work, if the SATA controller uses AHCI instead of something proprietary as is typical for SAS controllers.
>> NVMe
> Using proprietary connectors.
Not for the past decade; it's been no connectors for most products, but standard PCIe connectors for the Mac Pro, and NVMe over Thunderbolt works fine.
>> XHCI
> Not on Lightning.
Again, not relevant to any recent products. And I'm pretty sure you're misunderstanding what XHCI is if you think anything with a Lightning connector is relevant here (XHCI is not USB 3.0). You can connect a Thunderbolt dock that includes an XHCI USB host controller and it works out of the box with no further driver or software support. I assume you can do the same with a USB controller card in a Mac Pro.
>> AHCI
> How exactly would Apple not support AHCI?
This might be another case of you not understanding what you're talking about and are lost in an entirely different layer of the protocol stack. Not supporting AHCI would be easy, since they're no longer selling any products that use SATA, and PCIe SSDs that use AHCI instead of NVMe died out a decade ago. But as far as I know, a SATA controller card at the far end of a Thunderbolt link or in a Mac Pro PCIe slot should still work, if the SATA controller uses AHCI instead of something proprietary as is typical for SAS controllers.