Umm, makes me wonder why it shouldn't be accurate in the first place. Sounds like they had no trouble fixing the problem. I know some factors are part of that but still.
Only significant variable is tire circumference. The error should be almost zero for the original OEM tires from the factory. Replacement tires are another story.
Honda cranks in an intentional error biased high. Yamaha does the same thing on the FJR.