Hi, I recently came across an issue where the display refresh rate suddenly drop from 120hz to 60hz during phone wake up/unlocking animation and causing unpleasant jittery screen transition. I became aware of this issue after noticing a stuttering and jerky motion when unlocking the phone. At first I thought it was just in my head, but upon turning on the "show refresh rate" in the dev mode, it became apparent that the phone does indeed experience frame drop during the animation. After a bit more testing, I figured out the general behavior of motion smoothness, where the phone will amp up to 120hz when you touch or use the screen and after a few seconds of inactivity, the screen will lower the refresh rate back to 60hz. The phone will not switch the refresh rate when used at low brightness and will stay at 120hz consistently. This allows for smooth user experience, while also saving battery.
However, I believe that the sudden switch in the fps during the phone unlocking animation is due to an unintended bug, rather than for power saving purposes. This is because the fps drop will NOT occur if you lock the screen after using any app and/or when you change any settings. Here the animation will be stutter-free (runs at 120hz through the whole unlocking animation) for the first or second time you unlock your phone, but will resume to be laggy after the the 3rd or 4th time.
It would be very nice if Samsung can take a look at this and optimize the motion smoothness option a bit more.