As evidenced by the above comments, insurance companies don't necessarily go by the vehicle manufacturer's marketing classification. They have their own methods and formulas for defining the classification of a particular vehicle.
The make, model and manufacturer's own classification are variables, but so are engine size, number of cylinders, height, weight, horsepower, parts availability, and whatever else a particular insurance company decides is important to include in their formula.
So Yamaha can call it whatever they want, and insurance companies will go ahead and classify it however they decide.