The thing about betrayal is that the circumstances don’t matter, the end results don’t matter. The social contract is broken as soon as you act on going against your word. Harry and Ron are breaking the implicit social contract they have with the fellow members of their house by acting on their selfish urges. To that point, I have a great deal of sympathy for Hermione. She understood what being in a house meant, to uphold the values and work together for the greater good. Harry and especially Ron thinking of her as an arrogant know it all and treating her with disdain must have been hard to take.
Harry’s name preceded him and he was always looked at through the lens of the actions he had no control over. He must have felt an imposter in those first few weeks at Hogwarts and Flying must have been a much-needed relief for him. I’m sure it helped him feel comfortable in his own skin, to finally have something in the magical world come easy, and to be lauded for his own actions.