Agents are largely useless when it comes to advice on most aspects of FF program such benefits and earnings. DL stopped using ticketing carrier as a factor in earnings several years ago and now exclusively uses marketing carrier. Technically, GUC upgraded flights are supposed to earn based on original booking class. But since upgrades on KL book into a revenue class instead of a dedicated upgrade booking class (OY on DL coded flights), I believe they will generally credit as if they are revenue KL Z fares.