Just to add to this, when I was heading from the aircraft to the bus through flight connection to other terminals I was asked to prove that my flight was leaving from T4 - I had a boarding pass, but had to show some documentation that the flight was leaving from T4, thankfully this is listed on the QR app, but not on the itinerary I have for my flights (which I had a printed copy of) this added a couple of minutes whilst the app loaded and I found some supporting documentation.