ValidationAssist.Suppress does not affect textbox underline

I am using the following style to suppress validation on disabled textboxes.

    <Style x:Key="DefaultTextBox" TargetType="{x:Type TextBox}" BasedOn="{StaticResource MaterialDesignTextBox}">
        <Style.Triggers>
            <!-- Remove the errors when the control is disabled. -->
            <Trigger Property="IsEnabled" Value="False">
                <Setter Property="materialDesign:ValidationAssist.Suppress" Value="True"/>
                <!--<Setter Property="BorderBrush" Value="{StaticResource MaterialDesignTextBoxBorder}"/>-->
            </Trigger>
        </Style.Triggers>
    </Style>

Here is the result of that:

The red underline is still applied to the disabled textbox. The Error text is correctly hidden.

I worked around this by using the commented out setter for the BorderBrush. This is mostly just to make the behavior consistent with other controls. The Combobox does not require the workaround. I haven't tested any other controls either so it may be worth checking each one.

Start by reproducing the supplied XAML style with a disabled TextBox that has a validation error, then compare its validation styling with the ComboBox behavior. Trace the TextBox validation template or styling and verify that suppressing validation also removes the red underline while preserving the hidden error text.