Eu tenho um Clickable-Gridview em um HubSection:

<HubSection >
                    <DataTemplate>
                        <GridView IsItemClickEnabled="True" ItemClick="Hub_OnClick">
                            <RelativePanel >
                           <TextBlock Text="NiceText" />
                            </RelativePanel>
                        </GridView>
                    </DataTemplate>
                </HubSection>

Agora, sempre que eu clicar nesse hub, uma borda azul aparecerá ao redor do GridView (SelectedBackground).

No LiveVisualTree, mostra-me que a borda é de um controle "ListViewItemPresenter" dentro do GridViewItem. Portanto, modifiquei o estilo do controle original e colei na marca Page.Resources.

<!-- Default style for Windows.UI.Xaml.Controls.ListViewItem -->
<Style TargetType="ListViewItem">
<Setter Property="FontFamily" Value="{ThemeResource ContentControlThemeFontFamily}" />
<Setter Property="FontSize" Value="{ThemeResource ControlContentThemeFontSize}" />
<Setter Property="Background" Value="Transparent"/>
<Setter Property="Foreground" Value="{ThemeResource SystemControlForegroundBaseHighBrush}" />
<Setter Property="TabNavigation" Value="Local"/>
<Setter Property="IsHoldingEnabled" Value="True"/>
<Setter Property="Padding" Value="12,0,12,0"/>
<Setter Property="HorizontalContentAlignment" Value="Left"/>
<Setter Property="VerticalContentAlignment" Value="Center"/>
<Setter Property="MinWidth" Value="{ThemeResource ListViewItemMinWidth}"/>
<Setter Property="MinHeight" Value="{ThemeResource ListViewItemMinHeight}"/>
<Setter Property="Template">
  <Setter.Value>
    <ControlTemplate TargetType="ListViewItem">
      <ListViewItemPresenter
          ContentTransitions="{TemplateBinding ContentTransitions}"
          SelectionCheckMarkVisualEnabled="True"
          CheckBrush="{ThemeResource SystemControlForegroundBaseMediumHighBrush}"
          CheckBoxBrush="{ThemeResource SystemControlForegroundBaseMediumHighBrush}"
          DragBackground="{ThemeResource ListViewItemDragBackgroundThemeBrush}"
          DragForeground="{ThemeResource ListViewItemDragForegroundThemeBrush}"
          FocusBorderBrush="{ThemeResource SystemControlForegroundAltHighBrush}"
          FocusSecondaryBorderBrush="{ThemeResource SystemControlForegroundBaseHighBrush}"
          PlaceholderBackground="{ThemeResource ListViewItemPlaceholderBackgroundThemeBrush}"
          PointerOverBackground="{ThemeResource SystemControlHighlightListLowBrush}"
          PointerOverForeground="{ThemeResource SystemControlHighlightAltBaseHighBrush}"
          <!-- here -->
          SelectedBackground="White"
          SelectedForeground="{ThemeResource SystemControlHighlightAltBaseHighBrush}"
          SelectedPointerOverBackground="{ThemeResource SystemControlHighlightListAccentMediumBrush}"
          PressedBackground="{ThemeResource SystemControlHighlightListMediumBrush}"
          SelectedPressedBackground="{ThemeResource SystemControlHighlightListAccentHighBrush}"
          DisabledOpacity="{ThemeResource ListViewItemDisabledThemeOpacity}"
          DragOpacity="{ThemeResource ListViewItemDragThemeOpacity}"
          ReorderHintOffset="{ThemeResource ListViewItemReorderHintThemeOffset}"
          HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}"
          VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}"
          ContentMargin="{TemplateBinding Padding}"
          CheckMode="Inline"/>
    </ControlTemplate>
  </Setter.Value>
</Setter>
</Style>

Mas isso não está funcionando para mim. A borda do fundo selecionado ainda está azul. Mas por que? Onde está meu erro?