it's in the conversion (you are converting from kg/cm to oz/cm when you want oz/in)

The conversion from oz to kg is 35.27 oz/kg
the conversion from cm to in is 2.54cm/in

therefore, by my calcs, the servo should be doing ~180 oz/in

13kg * 35.27 oz/kg /2.54cm/in = 180 oz/in

It is probably overrated. What is your definition of "better steering"? speed? turning radius? torque?