Yes, that's right, that's a tutorial that seems to be about NVMe and IRST. They are basically just showing that the normal tools work. About IRST in general, here's a document where Intel explain what they did to Linux:
In the kernel, there's drivers for the controller in AHCI mode, RAID mode, and using NVMe drives directly. The user software RAID tools were extended to be able to use the structure on the drives that Intel's RAID wants to have, and to see what the Intel firmware shares about what's done in the BIOS menus.
I'm confused because everything is supposed to work. That's why that other explanation feels like it makes the most sense. I mean that explanation that Lenovo is configuring the controller to use a third, alternative mode that it has besides its normal AHCI and RAID modes, where the normal drivers then don't get attached to the device. About why that's done, the explanation would be that Lenovo wants to force the use of their customized driver. Then again, why they would want that makes no sense. It could just be a stupid manager asking engineers for something stupid, not a sneaky method to force Windows 10 onto the laptop.