That's how this works.
I got AW3423DW and I am fully expecting it to last maybe 4 years at most before I'll have to demote it to a secondary monitor because of burn-in.
OLED 100% burns in, as I can attest from 2 Samsung phones I have in the family - Galaxy S20+ where burn it developed after a year and a half and was so sever I opted to replace the screen (second screen seems to hold well so far since) and A50-something that also has visible burn in.
I hope AW3423DW will last a bit more, I try to babysit it as much as I can - did everything I can to mitigate burn-in potential, but I know that in the end it will happen, so I am calm about it - I know it's a product with expiration date.