It is possible that the tool (Asus StepUp) is increasing the voltages, thus enabling a stable overclock.
As to why stock clocks produce errors, I have no idea, considering I would assume everything to be running at stock voltages which should be sufficient.
The stock voltage with the Asus Rampage Formula shows 1.12V and with no load and 1.2v at load, with my other Mobo Asus Striker II Extreme it stays almost all the time at 1.2v
When clocked the voltage goes to 1.2 no load. I have tried to increase the voltage at stock speed but up to 1.21 I had only errors.
Have you tried running the test on stock clocks with the power saving functions turned off? Perhaps they introduce some instability with the torture tests?