Hello, thanks for the follow up on your arrival and departure experience.
Migration officers do not need to scan your QR code for either arrival or departure, when they swipe your passport your e-ticket shows up on their screen (it's linked to the passport)
You will need your QR code mostly for arrivals, to show it to customs. For departure, customs won't normally ask any passenger for it, but it's a good idea to have it on your phone in case your bag is inspected or if you have something to declare when leaving the country.