Recently I lost my iPhone 8 on iOS 14.5.1 and I was using my iPhone XR on iOS 16.2 for longer than usual. I started developing weird headaches that I didn't experience for a long time.
Anyways, I managed to secure another iPhone 8 on iOS 14.5.1 and my symptoms subsided. It seems like being PWM-free alone is not enough for me and it also suggests that there is definitely temporal dithering on my iPhone XR on iOS 16.2. It's caused either by the panel itself or the OS rendering pipeline.