From earlier rumors, we were already privy to the information on the 240fps full HD from a code leak that showed it as an option on the new iOS beta. There was also a secondary rumor that stated 480fps on HD 720p as a code snippet. On the final phones, there seems to be no mention of this extra frame rate which possibly is being saved for a future mobile product by Apple.
The new Phones X (for ten) and 8 with the 8 Plus both have the same improved camera modules with the new A11 Bionic chip which brings new levels of performance to smartphones which also permits the processing of a larger frame buffer for full HD 1080p at 240fps and as an extra bonus for the first time in a Phone, 4k 60fps recording.