120 Hz reduces the nominal refresh interval from 60 Hz’s 16.67 ms to about 8.33 ms. Display refreshes, app-produced frames, and distinct frames presented are different counts. This article uses a historical Perfetto trace to explain their relationship and the rendering/power trade-offs.

Part five covered Choreographer callbacks; here the focus is the shorter display cycle. The screenshots describe that capture, not every 120 Hz device’s scheduling configuration.