Im not sure which spinner they were refering to, but the only one im aware of is Vern Juenke's.
You can contact him at:
THE ACCURACY DEN
Vern S. Juenke
25 Bitterbrush Rd., Reno, NV 89523; (702) 345-0225
It essentially spins the case or bullet around its vertical axis, and measures the imbalance of the bullet or case being measured in deviation units.
Hold onto your wallet though.... they are steep. $840 last I heard.
I know its repeatable, the same bullet will measure the same number of deviations every time so it is measuring something. Variations in case wall thickness or bullet jacket thickness, combined with how out of round the object being measured is....but im not sure its ever been proven that the bullets that tested best always shoot the best. On the other hand, some of the top guys in the 1K BR game sort bullets on this machine, and some spin brass as well.
Who knows!