No, there is no current rule like that for the twins. The HD XR750 has been racing 40 years and there is no production version, though they've tried a few times. The new HD XG750R isn't production based either. There is a proposed rule change for the 2020 season to allow only production engines. Plenty of time to change the rules between now and then, and it may just be a production class in addition to what they have now.