I'm not sure, frequency is only important if you are going for resonance, and you can't make a tubular array resonate,
If you want to understand how the amps are restricted in a dead short condition you need to learn about Inductance reactance. In the last few days I did quite a bit of reading on this to understand how the chokes work, and it really makes a lot of sense.
Basically, it comes down to the fact that voltage across and current through an inductor can not change in zero time, so when the chokes are pulsed and the water is in a dead short to the ground there is an inductor in between prevents the current from rushing in. Also if you read about dielectric breakdown you'll learn that when the dielectric fails, all the voltage is transformed into a surge of amps, but this can't happen in the wfc because the chokes prevent this surge of amps. It's all quite simple and brilliant when you start to understand how he is using simple electrical principles to accomplish what he needed. I still have much to learn, but it's coming nicely.
When ever he says "tune into the dielectric properties of water" I think this just means using it as a capacitor in a resonant circuit, and of course it is a liquid dielectric, and he is bringing it to dielectric failure, preventing the amp surge, and allowing the dielectric to recover, as you can read about for liquid/gas dielectrics. Also when you increase the voltage significantly, this changes the dielectric properties of the water, as he talks about in the Switzerland video, he definitely emphasizes the statement that water is a "dielectric liquid".
