For RAID hardware, it's not that unusual to have a device that isn't supported by standard Windows install media. To install Windows, you'd put the Intel-provided driver on another medium (or slipstream it into the Windows one), and click "load driver" in the installation GUI.

Lenovo apparently wants to treat that computer as an appliance; if someone borks their installation enough that even a system restore won't fix it, it's a call to Lenovo support, and a bill if the machine's out of warranty.

For customers whose Windows installations are working correctly, it's access to a faster, more power-efficient driver. That's how it makes sense, IMO.