I forgot where but there is a photo or video somewhere apparently taken with a fast shutter speed showing diagonal bands on the screen of a Pro1 indicating it indeed does PWM to dim the display (as you'd expect). Most AMOLED are modulated at 240hz so that's my best guess at the frequency. Personally haven't had any issues staring at AMOLED screens and the likes, although i can perceive it when waving a hand in front (instead of a smooth motion blur i will see stepped type motion blur ish something, if that makes sense).

If this concerns you it's important to know most LCD displays also use PWM to dim the backlight and on some LED backlights that does translate into flickering light, and sadly manufacturers generally will not tell you whether or not this is the case so it can be tricky to find the right thing to buy. The same issue exists if you buy LED light bulbs, and there it does bother me sometimes (not that I get headaches or so but I find it not pleasing to my eyes)... Edit: additionally for LED bulbs for room lighting, they usually flicker at 100/120hz which makes the effect more perceptible.