Odometer and a speedo stepper motor are 2 entirely different things. Think about your gauges sweeping to 185 mph every time you power the gauges up, this doesn't get counted as any distance. The dash is performing 2 different things based upon 1 input. Speed square wave signal in, odometer out, and speedo out.
If I get time this weekend ill prove the theory.
Now on a gen3 (not possible on gen1 or gen2), I can make my odometer not increase at all when running 185 mph for hours at a time, and I can make the odometer act like I am going 200 mph when the speedo shows 1 mph.