I would say that half of my monitor, more accurately, is about the dimensions of an iPad at comfortable viewing distance.

Phones are far taller than half of a 1080p screen.

Half a monitor is: 960 x 1080, or 1:1.125 A iPhone is: 828 x 1792, or 1:2.164

So websites tend to shove a candybar shape into a nearly square sheet of paper and waste a lot of usable proportions for things like controls or hamburger menus.

Not GP, but yeah, about the same? From your phrasing I expect it's how close we hold our phones that differs though.