Just checked it's 1080p portrait mode for PC not Landscape. So unless you want to play the game with your head sideways I'll see if there's an option in the config to change it to widescreen and post what you need to add into that file.
Just found a semi-easy fix. Take it out of fullscreen mode and drag the side of the window until it's in a similar portrait mode shape to the preview images. That should work and give the same scale as if it was landscape. Albeit without a background.
