Not sure what you mean here, but according to Cynthia, Dragonite didn't listen to Iris in the World Tournament Junior Cup because it didn't trust her enough. This continued until Iris and friends fought against Team Rocket, when Dragonite started to listen to Iris to get Meloetta back.
I'm with you Plat I don't see the point either. Dragonite never "betrayed" Iris, it just wasn't in tune with Iris because it didn't feel it could trust her or anyone for that matter. Not to mention it felt strong in its own right that it fought on its own pride instead of listening to its own trainer.