ToggleButton's Style.Triggers works only when ToggleButton's Style is set to "ToggleButtonCustom"

I'm trying to change the tooltip of a ToggleButton when ToggleButton is Checked/Unchecked using Style.Triggers as shown in code below.

<hc:ButtonGroup Margin="4,0,0,0" Orientation="Horizontal" Style="{StaticResource ButtonGroupSolid}" hc:BorderElement.CornerRadius="4" hc:BorderElement.Circular="True">
	<ToggleButton>
        	<Path Data="{Binding Source={StaticResource PerspectiveViewCube}, Path=Data}"  Height="15" Width="15" HorizontalAlignment="Center" VerticalAlignment="Center" Stretch="Uniform" Fill="Gray" Stroke="{DynamicResource PrimaryTextBrush}"/>
                <ToggleButton.Style>
                	<Style TargetType="{x:Type ToggleButton}" BasedOn="{StaticResource ToggleButtonBaseStyle}">
                        	<Setter Property="ToolTip" Value="Turn ON Perspective View"/>
                                <Style.Triggers>
                                	<Trigger Property="IsChecked" Value="True">
                                            <Setter Property="ToolTip" Value="Turn OFF Perspective View"/>
                                        </Trigger>
                                </Style.Triggers>
                	</Style>
                </ToggleButton.Style>
        </ToggleButton>
</hc:ButtonGroup>

But its not working. The ToolTip is not displayed wether the ToggleButton is checked or unchecked. But if I set the style using BasedOn="{StaticResource ToggleButtonCustom}" it works. For any other Style it doesn't work.

Start with the ToggleButton style definitions, especially ToggleButtonBaseStyle and ToggleButtonCustom, and compare how they affect the control's ToolTip and Style.Triggers. Reproduce the XAML example with checked and unchecked states; done means the tooltip changes for both states regardless of which supported base style is used.