How to initialize the window size to span multiple screens

stabbles

Currently it seems impossible to initialize a Window with a size greater than the current screen's size. Consider the MWE:

import QtQuick 2.12
import QtQuick.Window 2.12

Window {
   visible: true
   width: Screen.desktopAvailableWidth
   height: 300
   title: "Hello world"
   onWidthChanged: console.log(width)
}

With two full-HD screens (twice 1920px wide) the output is

qml: 3840
qml: 1920

So basically the window is initialized to 3840px and then immediately resized down to Screen.width aka 1920px.

I can however manually resize the screen to span multiple windows, why can't I do this programmatically?