My experiences with OLEDs has been quite inconsistent. But I do not think the polarisation has changed. It seems that PWM in OLEDS affects me a lot, despite not affecting me in other devices (I have an LED LCD TN laptop which uses low frequency PWM that I can use ok).
I think the reason I could use the S3 mini was its small size, and favourable PWM (not tested though), but I still can only look at it for a few minutes before pain develops. All the other samsung devices have been much worse, older or newer, I assume due to their aggressive PWM.
One reason I suspect polarisation is a problem for me in general, is that even completely PWM free OLED phones like the LG Flex 2, and Lumina 650 cause me discomfort. But to a much lesser extent than the others.