Placebo effect, at least for vertical compliance. No human is sensitive enough to detect the vertical compliance difference between two identical rims, laced to a high- and low-flange hub.

Not really that hard to do. I was tensioning by ear in the 1970s, a technique I learned from my dad (who built wheels for Jobst Brant in the early 1960s, including some interesting tubular wooden rims that Jobst wanted). Tap each spoke with the spoke wrench, listen for the note. My wheels stayed true.

Thin spokes are "exotic" because wheel building machines have trouble tensioning spokes that thin--they tend to wind up when tensioned. Not a problem when tensioning a wheel by hand.