Not entirely true, from my experience.
The rods are not an electronic device, they don't really do anything. My understanding is that it's the user who is making them work. Without a skilled user, they are just bent pieces of metal.
The sensitive I worked with claimed that it was her spirit guide that moved the rods. The entity that my SLS camera clearly showed as manipulating the rods. She asked it what rod movement signifies yes, (usually crossing), what signifies no (usually diverging). She then asked her questions and got answers she could understand.
The EVP right afterwards also added to the evidence.
I used to think it was just a "water-witching" tool, but no longer. The rods serve as some kind of antenna or dial on a meter, but it does take a certain person to wield them correctly.
Your mileage may vary.