With the release of the iPhone 13 Pro and Pro Max, Apple finally introduced high-refresh screens on its flagship phones. To be more battery efficient, the implementation of the feature on iOS is different from that on iPads with similar screens in the past, but it turned out to cause problems. Apple has now promised to update its phones to fix this.
By default, most third-party apps are locked to 60Hz right now with 120Hz, which only kicks in for some animations and scrolling. In fact, there is a bug that limits some Core Animations to 60Hz, so a future patch would fix that as well.
Apple has already released documentation with instructions for developers and how to update their apps to enable ProMotion on the iPhone 13 Pro and Pro Max. There is even a list of supported refresh rates and times.
