As usual, we can only guess, and try to find a needle in a haystack. I've been also thinking about refresh rates, frequencies, etc. For example I have some ear issues where particular frequencies tend to cause me physical pain (probably due to many years with headphones, etc.). There seems to be a relation between eye strain, sinus / jaw issues in some cases, both of them have also effect on ears. The pressure I can feel from staring at some laptops resembles sinus pain. So maybe our eyes are sensitive to specific frequencies, the same as ears, and these frequencies might have changed in recent years - due to dithering, new technology, more powerful gear, etc. Since we have different sight we may be sensitive to different frequencies - that would explain why someone can't use PWM screen with low refresh rate, while it doesn't bother other people. Just a thought, one of options.