I can tell you this, Intel found a way to prevent this from working, by a change/update in what is called the processor's microcode. That is normally done in a BIOS update, or can be done manually if you know how to do so. I'm not sure if there is another way Intel could sneak in a microcode update, such as in a chipset firmware update (IME firmware for example) or driver update, but I've seen nothing about that.
Since Intel does not want Non-Z OC to be available, and all mobo manufactures have figured it out, Intel wants them to put the microcode update in a BIOS update. Occasionally you will see a BIOS update that mentions a CPU microcode update that is done for another reason. Of course, a mobo manufacture is not required to tell you what is contained in a BIOS update, so it could be in one and we'd not know... until the Non-Z OC feature suddenly doesn't work anymore.
Let's look at the BIOS updates for the ASRock Fatal1ty H87 Performance board, that was said to have this feature:
ASRock > Fatal1ty H87 Performance
We can see the BIOS version 1.50, dated 7/8/2013, lists adding support for Non-Z OC. This board does not have any BIOS updates beyond 1.50, so that feature has not been removed, or contains the microcode update that would override this feature. So, Non-Z OC should be working. If a board like this had newer BIOS updates, and one of them mentioned a "CPU microcode update", you probably would want to avoid using that version, if you wanted the Non-Z OC feature.
We can understand at least why mobo manufactures are not talking about this feature anymore, but if you know what to look for, it still seems to be there. Any board that you are wondering about?