I think their onboarding screen doesn't do to great of a job at explaining how the feature works. If the app only sends notifications after being explicitly asked to do so by the user, the text should reflect that. (something like: "You can mark flights you want to buy tickets for, and the bunny will send you a notification when they have the best price. We won't send you any other notifications.") It sort of hints at it, but doesn't spell it out clearly.