The official memory specification this processor supports is DDR3-1333/1600MHz rated at 1.5V only:
We will make sure your comment reaches the proper department for future consideration.
As an experiment I tried lowering the memory voltage down to 1.5V to see if it still worked, and it did. The agent voltage needs to be at 1.050V though to get it to run at 1866mhz. For some reason, in the bios Performance Summary it says the memory is still running at 1333mhz even though the multiplier is at 14, but everywhere else in bios (including classic mode) it says 1866mhz. I guess that's another bios bug apparently, but from all I've seen elsewhere, even in AIDA64, it's indeed running at 1866mhz (or 933mhz x 2).