It's not just a matter of firing all cores,it's the fact that the CPU only ramps up to that clockspeeed when certain benchmark apps are detected. It doesn't ramp up as high when doing other tasks,that why it's called cheating.

The thermal headroom is raised by pushing all cores to run at 2.3GHz as long as the benchmark app is detected but it's not raised when you use other apps so that it doesn't kill battery life or doesn't overheat making it not a representative of real world performance. Geekbench is supposed to simulate real world app performance [it gets it's scores by running apps] . This makes one expect the device to perform on a level matching it's benchmark scores when it reality it won't perform that way due to thermals,battery etc etc.

An analogy is like when you buy a pc graphics card expecting a certain level of performance after seeing benchmarks done only to find out later that the card only performs that good in benchmarks,not in games. If that's not cheating then I don't know what it is.