This issue should be resolved in the upcoming iOS 17.4 release: 257862 – accelerated animations not running at 120fps on pro motion devices
I verified that Ionic’s animations run at up to 120fps on supported devices. Note that swipe to go back is still capped at 60fps because touch events are dispatched at that rate. However, playing the page transition (without the user swiping) will run at up to 120fps.