I don't get why Samsung would make these an OEM exclusive. It seems to me that aftermarket enthusiasts would be the major purchasers.
What OEM would even use these? Most OEM SSD options are low grade entry level SSD. Apple is the best I've seen, using the Samsung SM951 in a proprietary form factor. The highest I've seen any other OEM use is the Samsung PM951 (Dell XPS laptop, MS Surface, Lenovo Yoga 900).
Do these just show up in high end workstations or servers? So far the only manufacturer I'm aware of whom would likely include these would be Apple. If they ever get off their butts and update their premium priced yet obsolete hardware.
As manufacturers are hesitant to boast in their specs what SSD they use. How would you even know without purchasing the computer or finding a teardown that the SM961 is in there?