...but the rule I'm talking about - is GENERAL, for devices using transistors 
For FPGA, the power scales linearly with clock.
https://www.researchgate.net/figure/Dynamic-power-consumption-vs-processor-clock-rate-measured-on-Spartan-3-FPGA-The-number_fig7_258762660
but that's relatively low frequences there
a real test would be to set frequency @ 500MHz by whitefire and see an overall power consumption, then