The Light Mode is still (by tratition) the default, Dark Mode ist optional
As a user I'd like MicroStation to behave in its apperance the way I have configured Windows.
If Windows ist set to ligth mode, then MicroStation shoudl by default start in light mode
If Windows ist set to dark mode, then MicroStation shoudl by default start in dark mode
If Windows is set to UserDefined then MicroStation may start in light mode by default
Either way the user choice should be possible any time