Digital Foundry is back again, this time with Xbox One exclusive Halo 5: Guardians. The outfit checked out the 'Gold Master Code' version of the game, where they noted that during their testing, it stuck very closely to 60FPS.
They noted that 60FPS was maintained throughout the testing apart from a few scenes where it dipped ever so slightly, but one of the bigger things they noticed was the HUD design/helmet overlay. The helmet overlay takes up far too much screen, and mixed with the super narrow field of view (FOV) - it most likely explains an element as to how 343 Industries were able to maintain 60FPS on the APU inside of the Xbox One.
Keep in mind that Halo 5: Guardians has a 'dynamic resolution' of 1080p, where it dynamically scales up to and close to 1080p depending on the on-screen action. The cutscenes are all rendered in 1080p with better anti-aliasing, but the frame rate drops to 30FPS. Full 1080p is "a bit of a rarity" for Halo 5 according to Digital Foundry.