Update: frame-by-frame measurements from 3 new recordings (Nov 5, 2026) I filmed my iphone 17 pro max(iOS 27.2) with a second iPhone at 4K 120 fps and measured content movement frame by frame. Capture timing was verified (8.333 ms median frame interval, no gaps over 12 ms), so no camera frames were dropped. A frame was counted as held when content stopped moving for a frame during active scrolling and then jumped forward to catch up. The alternating ~60 Hz cadence near the end of each deceleration was excluded, since it is likely ProMotion's intentional low-speed refresh rate reduction. Results (hitch time ratio = held frames x 8.33 ms / seconds of active scrolling): App Store app, Apps tab About 5.0 hitches per second, 6.7% of frames held 13 multi-frame stalls of 25-33 ms Hitch time ratio: ~67 ms/s In several fast-scrolling segments, content updated only about 80 times per second instead of 120 Third-party video app, feed list About 4.2 hitches per second, 3.9% of frames held Hitch time ratio: ~39 ms/s Third-party shopping app, search results About 3.5 hitches per second, 3.6% of frames held Hitch time ratio: ~36 ms/s For reference, WWDC20 "Eliminate animation hitches with XCTest" describes under 5 ms/s as good, 5-10 ms/s as warning, and over 10 ms/s as critical. All three recordings are in the critical range, at roughly 3.5x to 6.7x the threshold. Values are approximate, since the camera and display clocks are not synchronized. Original videos and frame-by-frame data are available on request.

Filed as FB25432914.