Quercus wrote:but it does make me suspect that dowsers sometimes pick up on *something* that means where the rods cross isn't just random chance. Whether that's […] surface features on the ground,
For a buried pipe, you dig a trench in the age-compacted ground, put the pipe in then fill in with loose earth that you may then machine-compact and regrade (optionally returfing/reseeding the whole area, or replacing the turf that you removed orior to the dig), but you've probably under
or over-filled by the time the surface has no visual signs. Minute changes in springiness of the ground is likely, and/or a bit of a depression or ridge. (Plus, you might see places, like main buildings/outbuildings or water storage ponds and tanks, where it's logical that a pipe leads between them.)
unremembered glances at other participants
That and noise-based feature enhancements. Subtle clues emerging across many different (literal!) 'random walk' similutaneous noisy scattergunning attempts to make datapoints will cause clusters to appear, and consistent clusters reinforce themselves as cues for further cluster-additions.
Or maybe it's just that i happened to notice "successes" more than "failures".
I imagine that when first given the rods/forked-stick on the edge of the designated area you're, like I have been, absolutely nervous of 'false' indications and think "I consciously did that, ignore, relax, go further", especially if yold that you're "trying too hard, relax"
only on false-positives (maybe "try that again!" when having false negatived), and you then you only start to 'accept' the twinges when you're more in the middle of where it's likely to be randomly right, and everything else comes to a head in reinforcing even the random correct-positives.
Or it's mystical. But likely not.

So… he wanted to build a rocket, failed to find anything like enough funding,
then decixed he was a Flat Earther just before tapping the donating-power of that community to finally build his rocket… Call me cynical, but I don't believe he actually believes what his current funders believe he believes. Well, apart from the "I want to build a rocket" part.
(Edit2: Ach, post-ninjaed while editing that in. See below!)