Hey aakshey
Stop telling this lies and say to people that your phones are defective. This is not a issue is normal behavior in oled iPhones. The phones in the apple stores has not the same software they put a software that modify the normal behavior of iPhones because of this you not see this behavior in apple stores , they not the same iPhones software that you have at home. They put full brightness in AB on and off to show all the brightness possible in the store. I check for my self and talk with a apple technician , ok .....
Stop with nonsense arguments and with this lies .
Don’t irritate me. Enjoy your iPhone.