I played full screen, I tried again and post a picture below. Unless of course I miss the full screen button, as I only see one, and I think I need to see one from Unitiy and one from Itch.io. I posted my game and made it so it will automatically go to full screen. I did found somewhere this is the best way to do it if you don't work with Unity.
*update, I see you posted something about it :). I think if you change like below your problem may be fixed.
