WindowsAppSDK: Content doesn't fill the entire screen when using FullScreenPresenter at a first time after app start

Describe the bug

When I execute at a first time

_appWindow.SetPresenter(AppWindowPresenterKind.FullScreen);

There’s two white thick borders on the Window at the bottom and the right sides. Bottom one looks like a Taskbar-size and the right one looks like a scrollbar-size.

When I restore Presenter to Default and then go Full Screen again, everything seems to be fine.

Steps to reproduce the bug

1. Create Blank App, packaged (WinUI 3 Desktop)
2. Create a Button on non-white-backgrounded Grid
3. Fill the Click event handler using AppWindow.SetPresenter (sample code below)
4. Run: Unpackaged, x64, Debug (other configurations didn’t tested)
5. Click the button

Result

The app went to full screen mode. Window’s content doesn’t fill the entire screen.

Expected behavior

There’re no borders. Window content fills the full screen.

Screenshots

Preview image on a full screen, it’s clickable. White borders on a white back are invisible (in case you’re using a light GitHub theme).

NuGet package version

1.0.0

Packaging type

Unpackaged

Windows version

October 2020 Update (19042)

IDE

Visual Studio 2022

Additional context

Reproducibility: 100%

Sample code, only changes to default template.

MainWindow.xaml

<Grid Background="CadetBlue" BorderBrush="Red" BorderThickness="2">
    <Button x:Name="myButton" Click="myButton_Click" HorizontalAlignment="Center">Full Screen</Button>
</Grid>

MainWindow.xaml.cs

public sealed partial class MainWindow : Window
{
    private AppWindow _appWindow;

    public MainWindow()
    {
        this.InitializeComponent();
        _appWindow = GetAppWindowForCurrentWindow();
    }

    private void myButton_Click(object sender, RoutedEventArgs e)
    {
        if (_appWindow.Presenter.Kind == AppWindowPresenterKind.FullScreen)
        {
            _appWindow.SetPresenter(AppWindowPresenterKind.Default);
            myButton.Content = "Full Screen";
        }
        else
        {
            _appWindow.SetPresenter(AppWindowPresenterKind.FullScreen);
            myButton.Content = "Exit Full Screen";
        }
    }

    private AppWindow GetAppWindowForCurrentWindow()
    {
        IntPtr hWnd = WindowNative.GetWindowHandle(this);
        WindowId myWndId = Win32Interop.GetWindowIdFromWindow(hWnd);
        return AppWindow.GetFromWindowId(myWndId);
    }
}

There’s no workaround found yet.

Also my default Windows theme is Light. If i set explicitly add RequestedTheme = ApplicationTheme.Dark; in the App ctor, the bug stops reproducing.