After reading about PWM, I feel sorry for those who suffer from this. I don't know if I suffer from this or not, I have an 11, but I have received headaches from my iPhones in the past, and two of the things that gave me massive headaches are True Tone and Reduce Motion. The Reduce Motion started for me way back when iOS 7 was released, all that animations or zooming in and out made me sick, I had really bad headaches and felt nauseated, and then Apple released a fix allowing you to turn that off and my headaches went away, like someone flipped a switch. So I have always had to turn on Reduce Motion. And when True Tone was released, that was another thing that messed with my eyes, had this problem on my 8 when I got it, when it was on, it was as if my eyes were struggling to read things and was causing me headaches. When I disabled True Tone, again it was if someone flipped a switch and my headaches went away. Makes me wonder what would have happened had I gotten the 11 Pro. After reading about PWM and knowing what my issues are with Reduce Motion and True Tone, I am actually glad AT&T did not have any Pro's in stock when I got a new iPhone or I feel I may be in the same boat as others.
I feel sorry for those who don't know anything about this and have headaches as a result. I know back when iOS 7 was released and I updated to it, my wife and friends thought I was crazy when I kept complaining of all the headaches I had, all over a software update. I am jut glad I can disable those two things.