如果父级样式在父级的Style.Resources中定义，为什么Style.BasedOn不适用于子控件的样式？

Question

我有风格：

<Style TargetType="Panel" x:Key="{ComponentResourceKey TypeInTargetAssembly={x:Type styles:CommonStyles}, ResourceId=ButtonsPanelStyle}">

        <Style.Resources>
            <Style TargetType="Button">
                <Setter Property="Margin" Value="5"/>
                <Setter Property="MinWidth" Value="75"/>
            </Style>
        </Style.Resources>

        <Setter Property="Background" Value="#E0E0E0"/>
        <Setter Property="StackPanel.Orientation" Value="Horizontal"/>
        <Setter Property="FlowDirection" Value="RightToLeft"/>
        <Setter Property="HorizontalAlignment" Value="Stretch"/>
        <Setter Property="VerticalAlignment" Value="Bottom"/>
        <Setter Property="MinWidth" Value="{Binding RelativeSource={RelativeSource Self}, Path=DesiredSize.Width}"/>

    </Style>

及其用法：

<DockPanel Grid.Row="3" Grid.Column="0" Grid.ColumnSpan="2" 
                   Style="{DynamicResource {x:Static styles:CommonStyles.ButtonsPanelStyleKey}}">
            <Button  Content="Add" Command="{Binding Add}" Grid.RowSpan="2" Height="23" HorizontalAlignment="Right" Name="AddButton" VerticalAlignment="Center" TabIndex="2" >
                <Button.Style>
                    <Style BasedOn="{StaticResource ResourceKey={x:Type Button}}" TargetType="Button">
                        <Style.Triggers>
                            <DataTrigger  Binding="{Binding ActionType}" Value="Edit">
                                <Setter Property="Button.Visibility" Value="Collapsed"></Setter>
                            </DataTrigger>
                        </Style.Triggers>
                    </Style>
                </Button.Style>
            </Button>
        </DockPanel>

应用于按钮的样式不考虑样式资源中定义的样式中设置的边距。为什么呢？