Eye strains are introduced by choppy motions where your eyes expect some moving object to be in one place, but it isn’t, so you have to jump further to where it lands and it appear again. Here I am just describing an example of a jumpy cursor that moves a lot faster than the display refresh rate, so you get the idea.
Also the “ProMotion” feature is just a PR term for variable refresh rate + a ”high” cap of 120Hz. We could argue if 120Hz is high enough but at least it is a really great number since it is a integer multiple of 2/3/4/5/6/10/12~, so in practical terms you get less uneven frame insertion which is also important to prevent choppiness. AFAIK, the MBP screens can go as low as 10Hz, and as long as Apple’s algorithm is not too aggressive in when to “power it down”, you should get a smooth transition throughout the UI even with frequent transitioning between fast and static motions. Though I can see the rather slow grey to grey response could be a problem here. Apple clearly made a conscious choice to give up on that front in priority for other perimeters.
Also the “ProMotion” feature is just a PR term for variable refresh rate + a ”high” cap of 120Hz. We could argue if 120Hz is high enough but at least it is a really great number since it is a integer multiple of 2/3/4/5/6/10/12~, so in practical terms you get less uneven frame insertion which is also important to prevent choppiness. AFAIK, the MBP screens can go as low as 10Hz, and as long as Apple’s algorithm is not too aggressive in when to “power it down”, you should get a smooth transition throughout the UI even with frequent transitioning between fast and static motions. Though I can see the rather slow grey to grey response could be a problem here. Apple clearly made a conscious choice to give up on that front in priority for other perimeters.