The focus was naturally scenes and "vibes" that couldn't be achieved with traditional films cameras. Boyle and Mantle weren't afraid to use whatever was best for the job, which included drones and other camera systems as well. More on their iPhone camera rigs for anyone who's interested:

https://www.ign.com/articles/28-years-later-danny-boyle-goes...

https://www.motionpictures.org/2025/06/how-28-years-later-dp...

https://www.wired.com/story/danny-boyle-says-shooting-on-iph...

Related: Driver POV footage for F1 was shot with Apple-created custom iPhone rigs as well.