I can tell you the drug sniffing dogs in use in Queensland, Australia in the late 2000s absolutely were basically “dowsing rods” (I was involved in illicit things at the time and went past/was sniffed by drug dogs over a dozen times and was never caught or searched despite having illegal drugs on my person, without much of an attempt to hide them). I’ve shown my partner how the handlers give a signal to the dogs to “mark” someone for a “probable cause” search too.