Who said anything about blocking current.
None other than Stan Meyers himself. He said many times ".... yada yada, Blocking diode..." and the diode is in every "circuit" diagram on the net.
This thread is titled "Back to Basics"
Did Stan Meyer show a circuit to anyone? The answer is no, he did not
V=IR
If you want to measure 20kV across water, which has a low resistance to electric current before electrolysis occurs, what do you suppose the amp level needs to be?
Obviously it can't be zero, can it? Otherwise voltage would be zero.
But it can't be high current either or you will have electrolysis instead of water splitting.
So how do you get high voltage with low resistance without getting high current?
KISS