"only in the " art " of dowsing can the novice or charlatan produce the same quality of info as the experienced and not get rumbled"
That's only in the type of dowsing where what is being found can't be otherwise found.
In the type of dowsing that involves finding stuff that can be shown to exist then no way can it not be tested, which is the point at which the reluctance kicks in.
It's like someone saying they can run faster than Bolt but no they won't prove it as negative vibes will affect the stop watch...