SystemBackdrop does not work correctly in multi window applications

[lhak]

Describe the bug

When using mulitple windows in the same application that both have the SystemBackdrop property set, switching from one to the other does not correctly deactivate the effect.

Steps to reproduce the bug

1. Run this repro project:
   MicaMultipleWindows.zip

2. Click on the button to open a secondary window

3. Observe, the the first window will still have the mica background applied. Only switching away to different applications deactivates the effect.

Expected behavior

Switching between multiple windows that use the backdrop effect should work correctly.

Screenshots

No response

NuGet package version

None

Windows version

Windows 11 (22H2): Build 22621

Additional context

Windows App SDK 1.3 stable

[codendone]

internal bug