Different screens have different PWM frequencies, so that may be it. Hard to say. My wife’s iPhone 15 bothers her much, much less than her 12 Mini. She uses it without needing to reduce white point.
On iPhones, the fix is to turn “Auto Screen Brightness” off, and use your screen at near max brightness all the time, which is where the OLED screen is flashing at the highest frequency.
Next, under Settings > Accessibility > Display & Text Size, turn on ”Reduce White Point”, and adjust the perceived brightness using the slider.
That’s it. Now you’re running your screen at max brightness (i.e. higher frequency) more often than before.
If you want to reduce brightness, then manually reduce the display brightness, as usual. No need to play with the Reduce White Point slider again.
The downside of this is that your screen brightness will ALWAYS be darker than it could be. Also, no auto-brightness.