Problem with the header style in Pivot?

### Describe the bug

Setting the header style globally does not display properly, only a single header per PiovtItem is OK

<Setter Property="Header">
<Setter.Value>
<DataTemplate>
<TextBlock Style="{StaticResource BodyStrongTextBlockStyle}" Text="{Binding}" />
</DataTemplate>
</Setter.Value>
</Setter>

。。。。

### Steps to reproduce the bug

1

### Expected behavior

_No response_

### Screenshots

### NuGet package version

Windows App SDK 1.7.3: 1.7.250606001

### Packaging type

Packaged (MSIX), Unpackaged

### Windows version

Windows 11 version 24H2 (26100, June 2025 Update)

### IDE

Visual Studio 2022

### Additional context

_No response_

No source file, test, or complete reproduction steps are identified. Start by reproducing the supplied Pivot and PivotItem.Resources example with Windows App SDK 1.7.3, then trace the Pivot header styling entry point. Done means the global header style displays consistently for every PivotItem and the behavior is covered by a regression test.

Written by the indexing model from the issue text.