I noticed something interesting: mpv was getting a reported refresh rate of
60.0hz in weston which is incorrect, actual display refresh rate is 59.951hz
(if I don't force it to 60.0hz as a workaround). In X, it gets the correct
refresh rate.

I was about to override the reported refresh rate to 59.951hz for mpv and play
a video without stutters, and without changing monitor's refresh rate.

weston-presentation-shm is also consistent with no vblank skips during playback
this way (at least with mpv playback). I suspect other applications are also
getting an incorrect reported refresh rate.