> Has anyone confirmed that this actually lowers power consumption when running MorphOS
> on a dual G5 PowerMac?

No.

> I wonder if both G5's ramp up to the same operating speed, when any MorphOS software
> demands more computing power from the one G5 CPU it is accessing? I would guess
> that the 2nd G5 remains at an idle speed constantly while running MorphOS

Both G5 CPUs remain at maximum clock speed constantly while running MorphOS.