Indeed, that is the way it works at thsi moment. When you are in Best Fit mode (CTRL-0) the space for the stage will always be filled, even if you close docking stations or resize them. But it will block other zooming features. I learned to use CTRL-1 to get back to 100% and then the zoom shortcuts are functional again. That checkmark next to 800% is clearly a bug, don't remember if I logged it already because I never use the dropdown menu for zooming.