The phrase "factory hitch" refers to a problem or issue that occurs in the manufacturing process of a product. It suggests that there is a flaw or mistake that happens during the creation of the item in a factory setting. Full definition
It also has the Class lii / Iv trailer towing package with factory hitch and wiring. (usedcarsgroup.com)
Payload and towing are both up compared to 2014 models: Maximum payload is 7,374 pounds, the best for any HD pickup, GM says, up from 7,222 pounds; maximum available conventional towing is 19,600 pounds with the available factory hitch, up from 18,000 pounds and also best in class, according to GM. (autoweek.com)
It doesn't have anywhere near the standard list of features that my Land Rover did (i.e. integrated factory hitch, rear mud guards, interior rear cargo cover) and it can't be purchased with other features (such as electronic traction control and front seat heaters) but.... (carsdesk.com)