Default NavigationView style from `Generic.xaml` is broken

Describe the bug

The default NavigationView style defined in Generic.xaml does not look identical with the ones without setting the styles.

Why is this important?

I want to re-template and still preserve the fluent design look and feel.

Steps to reproduce the bug

1. Copy the default NavigationView from Generic.xaml
2. Apply it like this:

  <NavigationView>
      <NavigationView.Style>
          <Style TargetType="NavigationView">
              <Setter Property="PaneToggleButtonStyle" Value="{StaticResource PaneToggleButtonStyle}" />
              <Setter Property="IsTabStop" Value="False" />
    ...

3. Observe the difference, especially the back button

Actual behavior

After style applied:

Before style applied:

Expected behavior

No response

Screenshots

No response

NuGet package version

WinUI 3 - Windows App SDK 1.8.3: 1.8.251106002

Windows version

Windows 10 (1809): Build 17763

Additional context

No response

Start by comparing the NavigationView style in Generic.xaml with the appearance produced when no explicit style is set, focusing on the back button and other visible differences. Confirm the copied template preserves the default Fluent look and feel when applied for re-templating.