Magnuson-Moss Warranty Act ban such stickers as the manufacture has to prove a modification directly led to the failure before denying a warrany claim. the FTC sent out in 2018[1][2] a letter to several manufacturers, including Apple I believe, that deployed such stickers on their products
The common example I give is that if you replace the radio in your car, and then the water pump fails the manufacturer of the car can not refuse the warranty because you change the radio
Similarly, if in this instance you remove the sticker to turn on Dev Mode and then the Screen fails it would be incumbent on Apple to prove some software or something you did directly cause the screen failure before voiding the warranty claim, they can not simply relay on a sticker
The common example I give is that if you replace the radio in your car, and then the water pump fails the manufacturer of the car can not refuse the warranty because you change the radio
Similarly, if in this instance you remove the sticker to turn on Dev Mode and then the Screen fails it would be incumbent on Apple to prove some software or something you did directly cause the screen failure before voiding the warranty claim, they can not simply relay on a sticker
[1] https://www.digitaltrends.com/computing/ftc-warranty-sticker... [2] https://www.ftc.gov/news-events/news/press-releases/2018/04/...