Yes, OLED does not used backlighting. But that is not the complete issue, most screen technologies can suffer from PWM. That is why you see some monitors advertised as “flicker free”. Those that are not flicker free are using PWM on the backlight. This wasn’t a big problem on CRT monitors because afterglow meant the backlight never went black between pulses. It got a bit worse with LCD screens, but became more of a problem when they switched from CCFL to LED for the backlights as they switched off so rapidly.
Despite what was said in post number 1, DC dimming is the solution, but it is hard to do on OLED.
PWM sends full power to the pixel (for OLED, backlight for LCD), but turns it on and off rapidly to control the brightness. The darker it needs to be, the more time it is off, and the more likely flicker will be an issue.
DC dimming sends just the right amount of power to illuminate to the level needed. The problem is quality needs to be very high, otherwise small variations between pixels becomes noticeable when trying to show the same colour.