Asus Z170-A Adaptive mode over-volts

Managed to get a stable overclock on an i5-6600k of 4.6 GHz at 1.325 V while having the core voltage set to 'Manual' mode. Decided to set it back to "Adaptive" mode assuming it would only undervolt and go up to 1.325 V. Which it did go down to 0.8 V while at idle, but it also started going up to 1.48 V under load according to CPU-Z, CPUID HWMonitor, and Intel Extreme Tuning Utility. So I don't think the software is wrong.

Is there a setting I'm missing or is the BIOS in the wrong?

Also a word of warning to other users, beware adaptive mode.