That's the way I see it, Ed. when using helical fetching and deliberately creating a spin. The spinning helps to tame the oscillations and the arrow gets on target sooner.
when the fletching is not offset, (or no other factor like the "wing" of the feathers causes the arrow to spin) then the flexing oscillations causes a different kind of spin.
If I take a arrow or fishing rod tip, and bow it slightly by pressing down in the middle while one end rests at 45 degrees on a tabletop, and then try to rotate it, I can often feel the stiff side. If I then place the stiff side up and push down, the rod wants to rotate a half turn when it bends.
my thought is that an arrow that spines more equally in all quadrants might need less fletching or less offset to stabilize. and perhaps why the hexshafts are preferred by some.