The measurements are not inaccurate. The calibration works.

Here's the deal: there is no such thing as a "perfectly white" white. It does not exist in and of itself. Perfectly white is whatever combination of red, green and blue we choose to define as "white". And that is the D65 white point. It's an international standard used by virtually all content creators. That means when an artist wants something to look "white", they make it look like the d65 white point. If they want a bluish white they'll skew blue and if they want a yellowish white they'll skew red.

Modern iPhone screens are the most color accurate in the phone industry, and by "most accurate" I mean that the default "white" they display (ie RGB 255,255,255) is the closest to the D65 white point.

However MANY phones and perhaps more significantly TVs skew wayyyy bluer than the D65 white point. That means every piece of content you watch is displayed to you much bluer than the artist intended. This results in the average person tending to consider an overly blue white as the "normal white".

If you have a NON DEFECTIVE iPhone, and you think it looks piss yellow, then you are subconsciously used to an overly blue white point. What you consider as "perfectly white" is NOT what the entire content industry considers to be "white". The problem comes from you.

It's either that, or OP's display is defective. It really is that simple.