Honda motorcycles speedos have been optimistic by about the same percentage for 30 years that I know of, most of the other brands are about the same. Although it's possible, I would really be surprised if it were any different.
On my bike, they could have just left the speedo off and lightened the bike up a bit. I don't remember my 1500's being as unreliable as the 1800. I use the GPS for speed refrence and when I want to calculate how much the speeding ticket is going to cost.