Because others conflate True tone Being to yellow, or, for those who don’t know what True tone is if it’s enabled, they think their phone might be defective with a yellow display. The iPhone has mainly been known for having a white, bluish, stark display, and True tone is a completely different type of feature correcting the white point based on the ambient lighting in the room. The shift to warmer displays started with the iPhone 7, as where the 6/6s were calibrated entirely different.