Window.ExtendsContentIntoTitleBar can't be set in XAML

Describe the bug

The Window class in WinUI 3 has a ExtendsContentIntoTitleBar property. However, it's not usable and requires a developer to set this in code-behind.

When set in XAML, the project does not compile throwing the following error: The XAML Binary Format (XBF) generator reported syntax error '0x09C4' : Property Not Found

THIS DOES NOT WORK

THIS WORKS

Steps to reproduce the bug

1. Create a new project
2. Open MainWindow.xaml
3. Set ExtendsContentTitleBar="True" in the Window object
4. Press F5
5. Error is thrown and does not compile.

Workaround

6. Open MainWindow.xaml.cs
7. Set ExtendsContentIntoTitleBar in the contructor.
8. Press F5

Expected behavior

This should just work in XAML as it's shown by IntelliSense and it's a property that can be set in code-behind.

Screenshots

No response

NuGet package version

WinUI 3 - Windows App SDK 1.7 Preview 1: 1.7.250208002-preview1

Windows version

Windows 11 (24H2): Build 26100

Additional context

No response

Reproduce the issue in MainWindow.xaml using the reported Windows App SDK version, then compare it with the workaround in MainWindow.xaml.cs. Check the XAML build error and property resolution; done means the property can be set in XAML and the project compiles successfully.