It's not made 100% clear which bits of the video here (click through to YouTube to see it maximum quality and resolution) were shot ON the iPhone 12 Pro Max, but some were clearly either done so or meant to be done so, and it's possible that the entire thing was also phone-shot.
Pretty impressive, really. I remember the first phones to shoot in VGA, then 720p, then 1080p (including the mighty Nokia 808 in 2013) and image processing power has now got to this somewhat crazy level where digital video can be captured in 10-bit HDR quality with real time (Dolby Vision) colour grading at 4K resolution at 60fps.
Emmanuel Lubezki here is shooting with the iPhone 12 Pro Max on a (DJI?) handheld gimbal, for comfort and extra stabilisation, although for most purposes the phone itself should be more than capable - it's just harder to hold securely (and artistically!)
I'll have the iPhone 12 Pro Max in for full review and imaging comparisons when it becomes available mid-November 2020. Watch this space.