The burgers at Jackson Hole are grilled with covers over them, producing a steaming effect that results in loose burger. They also have a grey appearance. It doesn't sound appetizing, but I've always found the burgers very good. I've never noticed any off flavors.
Sorry to be so vague YH, I would say different good or just different. Meatier? more barnyardy? As if there is a touch of offal in the mix? Old, but in a good way? I can't put my finger on it, but I do like it.