I've seen a few people mention this. The s25 does seem to use a lower pwm for the oled backlight. The issue is, only maybe 0.01% of people are affected by it, so I don't believe samsung will do anything about it.
For some suggestions, try settings, display, eye comfort shield, turn it on with enhanced comfort.
I'm not personally affected by the display so I can't test it. But enhanced comfort might help you.
Since you know about pwm you probably know how it works, for others in in case you don't, lemme say some things.
The brightness of the screen can't be dimmed. It is either full bright or full dim. So to make it some value between, it flashes very quickly. So 50% brightness would be the screen being dim for half the time. The human eye does some magic and you see it as half as bright. For some people, this doesn't go as expected. The brain doesn't like the speed and sorta gets confused, causing pain and discomfort.