1 lb on wheel is worth 2 lbs anywhere else that isn't rotating. But there's more...

That only works if you take the one pound off at the outside, like the tread or the belts in the tire. Take it off right in the center, & its only worth 1 lb. Anywhere else, like the brake rotor, its worth somewhere in between. That doesn't have anything to do with sprung vs. unsprung weight.

The UNSPRUNG weight is stuff that moves up & down with the wheel. Like the brake rotors, calipers, CV joints, etc. The entire body is SPRUNG weight. Parts of the shocks are sprung, parts are unsprung. You want to have lower unsprung weight, but that's for a different reason.