I'm talking specifically about the "Height" and "Width" parameters of the "Get Device Details" action. The pixel dimensions of my device are 1136 x 640, however this action returns 320 x 568. What are 320 and 568 – points, picas, mm?
I believe it's a Retina thing, where the actual resolution is x * y but the viewable/referenceable pixels are x/2 * y/2.
On my 11, the shortcut returns 896 * 414 which is half the official resolution. The lower resolution is referred to as the "viewport" size, I believe. (I'm not 100% sure as I've only just read about it myself!)