That is just a warranty requirement that Curt has decided to add for a lot of their Class I, Class II, and some Class III trailer hitch receivers which are rated for smaller towing capacities.
Because of this, I tend to recommend the Draw-Tite hitches like part # 75916 for your 2017 Volvo V60 or the Curt hitches, like part # C12066 for your V60.
For your V60, the Draw-Tite trailer hitch receiver is a Class III and has a higher weight capacity, 4,000 lbs, and tongue capacity, 400 lbs,... view full answer...
The two hitches you mentioned are very similar. The only difference is that the # 13266 is a Class III which uses the 2 inch square receiver opening and the # C12600 is a Class II which uses the 1-1/4 inch square receiver opening. Both hitches have a 3500 lb towing capacity, but the Class III has a tongue weight capacity (maximum weight that can be suspended from hitch without damaging anything) of 350 lbs, versus 300 lbs for the Class II. The Class II hitch will have a ground clearance... view full answer...