I see the CPU speed is being pushed again, what is noted may very well be overclocked and if you look at a block diagram the CPU is not the only important item. In fact many of the PCs you see listed are not built by them Skylake systems supported on Windows 7 and Windows 8.1 - Microsoft Support.
I have understood the limit on CPU speed is in the range of abt 3.5GHZ; the use of the 3 volt form them is based on thermal consideration. The devices do not operate on or off but go through a linear region and higher dissipation.
I would not be making a buy decision based just the test you noted but the total system and SKU version of the model and would never by a overclocked system, but tha is my bias.