2.7 Liter Ecoboost and 3.55 Rear ..5K Towing Capacity?

Hi all, So I was looking at a 2018 F150 CC with a 2.7 Liter Ecoboost and 3.55 rear. It has a payload rating of 1700 pounds. The dealer swears the truck only has a GCWR of 10200 and hence a 500...