Why are the dimensions of the artboard phones in the sketch 2 times smaller than the real ones?

Question

Design

Why, when choosing a new artboard in the sketch of any iPhone, then in its properties (on the right of the screen) the dimensions in pixels are exactly 2 times smaller than the real ones (see on the official website)?

Answer 1

Simply put, these sizes correspond to sizes in pt. The units of measurement were clearly written here https://habrahabr.ru/post/237931/
Many, but not all, consider it convenient to start drawing at 1x and then scale at 2x