Duly noted.

As I described in my essay, the iPhone X screen calculation is an example of how to grasp the concept of pixels, and how to be congnizant of pixel design thinking when using preset UI elements, and not how to build repsonsive sites where media queries are necessary.

Nothing in this article is 'utterly ignorant', as you mention. On the contrary, it is an approach to understanding the fundamental concept of pixel-based measurements.

The variation of pixels to EM/REM is a function every designer can implement once the concept of screen size is understood.

Design and development is a fluid understanding of how different levels of building apps and websites work. Understanding pixels is an important part of that.