"NVMe was not available until the 6th gen NUCs; the 5th gen NUCs only supported M.2 SATA SSDs."
Hmmm, someone must have missed to tell this to my NUC5I5RYK running Samsung PM961 NVME and my NUC5I5MYBE running Intel 600p. (ok, PCIe Gen.2 x4 is a bottleneck but its faster than SATA nevertheless)
NVME is supported in NUC 5th gen since 2015:
Release note for BIOS Version 0246 - RYBDWi35.86A.0246.2015.0309.1355:
• Added support for M.2 PCIe NVMe storage boot.
BIOS Version 0026 - MYBDWi5v.86A.0026.2015.0820.1501:
• Added NVMe information on the SATA page in BIOS Setup.