Not sure what the issue is but the game opens in a zoomed-in square window for me and cuts off the game's controls. Can't even see the "Exit Game" button it's cropped so closely :/
I'm running it on a 1440 monitor so that shouldn't be the issue. It definitely opens in a window much smaller than 1920x1080 on my machine though. Very odd.
I also had the same issue with the original build, on a 3-monitor setup with the primary being 2560x1440 (smallest screen is 2560x1080); don't know if that helps shed light on why.