Dealer's full of $hit. I can tell you with a great deal of certainty that the "edict" you mentioned did not come from HD. They can, as a service department insist on their product, but if you are supplying a like or better product they are then required to put their lube in at no charge. Being warranty work the replacement oil is a n/c item anyway, so if you feel you want the work done there dump it when you get home and put in your preference. Sounds to me like the service manager is trying to force a little extra commission this month as he gets a % of every HD product sold through his department.
The issue here is the "warranty" work I would imagine. As a DCX (Jeep) dealer if we do not replenish the fluids with "factory" fluid we do not get paid on warranty.
It goes so far as they monitor our oil purchase volume to make sure we actually buy enough from them to service our vehicles in operation.
I wouldn't see it as a problem if the occasional customer brought in their own stuff, but factories are getting more and more insistant on the use of their own stuff. We now get secret shoppers from them to make sure we are handling customers properly and servicing within the factory guidelines. Not sure that HD has gone to this but I can tell you that one of my manufacturers actually builds in faults in the car and sends a shopper in to see if we catch all of the problems and perform the service correctly.
I wouldn't put it past these guys (mine not HD)to go as far as having the oil tested to make sure it is the correct factory fluid. Since I sell Mob 1 in bulk, it isn't an issue for me as the factory stuff in this case is Mob 1.
Anyway, as much as there are some conspiracy theories here that hold water, there may be more to a dealer's actions than meets the eye in some cases.
If you bring your Jeep to me for warranty work, it's leaving with the MOPAR oil in it. I specifically stock it in quarts for doing warranty work. Otherwise, I'll put whatever you want in "your" vehicle on a regualar service.