I didn't read the whole paper and I'm no electrical engineer, but I'm also quite skeptical that this works. I'd probably believe it if current propagated infinitely fast, but obviously it doesn't.

My first attempt to tap into a channel with this system would be to tap into two points at some distance apart, then measure then changes in current at each point. Since the receiving resistor is flipped randomly and the sending resistor is flipped with the data, it seems to me intuitively that all you need to do to crack this is use a bit of basic electromagnetic physics to derive a formula to extract the data from propagation delays of the effective resistance experienced by the circuit measured at two distant points. I could be wrong though.