Very sure that it's not PWM flicker, that's just the panel's refresh rate. 😃
I stand corrected, ridiculous claim from my side, this is clear PWM dimming flicker. Huge error from my side.
But, even if this is flicker that you mention, there could be variance in panel manifacturer for the M5s, resulting in some that produce PWM flicker and some that don't.
That being said, considering Notebookcheck is the only reviewer that tests for PWM and dithering, it is the only reliable source for now to tell if phone display panels exhibit any glaring issues or not.
LTT is starting a phone division soon, so they might test for PWM.
Also, judging from the description:
Surprisingly, we don't see any of the typical flickering in our measurement with the oscilloscope, despite the OLED technology. There are at most some minimal high-frequency variations. This means that we are unable to find any pulsewidth modulation across the whole range of brightness settings. The effect is probably produced by a constant DC dimming in combination with a very high frequency*.* The likelihood of creating problems is at least lower with the Poco M5s than with OLED displays that use a low-frequency curve.
No OLED display is perfect yet imo due to the inferior pixel layout, low refresh rate and PWM-managed backlight across it's entire brightness range. LCD's are much better for normal use.