Check out this thread:
https://forums.macrumors.com/threads/pwm-on-new-baseline-2019-mbp.2189621/
It tends to be that the flicker is in the periphery of my vision and not directly where my eyes are focussed.
I have noticed a "PWM-like" flicker on the 2018 / 2019 models but not on the 2017. I am particularly sensitive to PWM however the PWM frequency of all the models 2017 to 2019 is around the same (120KHz) so shouldn't be a problem. My current thoughts are that intel is employing more aggressive dither in their latest drivers as I've seen Screens I was quite happy with (my Surface Pro 5) become painful to use following an update to the drivers. Rolling back seems to help. Unfortunately not an option on the Macbook.
I use my 2017 MacBook Pro 8 hours plus per day with no issue. I have a 2018 on the desk, identical specs (except the panel in A03E model instead of A034) and I get sore eyes after only 15 minutes.