I just got around to checking on my z170 Classy K's M.2 drive as well as DVD disks.  They all report being SCSI. Is this the way M.2 are?  I would think they are UEFI as the M.2 has what appears to be GPT (4 total) partitions.  So my, apparently miss understanding that the M.2 NVME would be some other interface type as in "NVME or UEFI)   

depends on the disk really, i have 4 drives in my pc, one nvme boot drive, it show the manufacture and part number, two seagate 3.5 sata 3 drives, they also show the part number also but my 2.5 HGST hdd i use for just image files show the manufacter, part number and scsi disk drive. this is all in device manager under disk drives. now if i go into properties and look the driver for all 4 says its from MS, in the event tab it shows them as scsi disk, i thinking it just has to do with how the manufacturs the drive for it to talk to windows and how MS writes the driver. oh BTW the 2.5 drive is on the marvell controller. but all are working as they should.