Liver and onions has been demoted, over the last fifty years, from a serious restaurant dish to a thing your grandfather ordered at a diner. Most American chefs under fifty have never put it on a menu. The dish requires a calf's liver sourced fresh enough that it doesn't taste metallic, a soak in milk to soften the iron edge, a hard sear that leaves the inside pink, and onions caramelized to the actual point of brownness.
Scott Calhoun co-runs Ember & Ash in Philadelphia with Dave Feola. Ember & Ash is wood-fired and is exactly the kind of room that would rehabilitate liver and onions on purpose. He brought the dish back from the dead and beat Bobby with it.
Bobby tried to elevate liver. Calhoun let liver be liver. The judges chose liver.