[skizzo]

I'd like to clarify bootrom 140 is what introduced the (native) NVMe bootability for "cheese grater" Mac Pros, the 4,1 and 5,1

cMP's are on 144 now or at least that is my latest version with 10.14.5 installer. It is THE BOOT ROM that gave the 4,1 and 5,1 Mac Pros the NATIVE ability to boot with a NVMe SSD

There are different sector type NVMe drives, Sierra could only boot ones that are not very common (512 bytes) . While High Sierra introduced the more common sector type (4Kbytes) making that adaption much more easy and widespread

Prior to that specific bootrom release, yes, all cMP owners needed to use some "hacks" to get it to work

I have been using a 970evo on High Sierra for almost a year. I just recently upgraded to Mojave.

Looked this up and 140 bootrom was introduced with 10.14.1 DP3 so this aligns with my estimated timeline of when I purchases a 970EVO for this specific reason.