Yes. https://support.apple.com/en-us/HT208191iPhones and cell phones use OLED screens and you guys are saying it's normal for OLED screens to burn? Lol.
OLED looks amazing and has a lot of fantastic characteristics but literally every pixel has finite life and consumable brightness. Display engineers move mountains on smartphones to mitigate and compensate for the effects of burn in but that is usually in the form of shifting color or peak brightness.
That is all I am at the liberty to say.