Chris, your comment about legacy systems also triggers a question about legacy support in NVMe drives. At work we had upgraded the boot drives of several systems that did not have UEFI NVMe support using Samsung Pro 950 or Plextor M8Pe ... because those two drives still have Option ROM that allows booting with Legacy BIOS. While I'm certain this is NOT a growing upgrade market for the latest NVMe releases, but it has been a great option for us keeping usuable hardware in use longer. And, given that NVMe is getting closer in price to SATA all the time, we would rather update older/recent hardware to NVMe than continue using the SATA devices.
Samsung dropped the Option ROM starting in the 960 series, and I'm not sure if Plextor's latest still carries it. But, is this something you have visability into, of all the drives you test, do you know or not if they have Option ROM included that would allow Legacy BIOS booting?