Developing layout web parts - documentation example

In documentation for Kentico 8.2 I found article "Developing layout web parts". In step 7 is following code:

if (IsDesign)
{
    Append("<table class=\"LayoutTable\" cellspacing=\"0\">");

    if (PortalContext.IsDesignMode(this.ViewMode))
    {
        Append("<tr><td class=\"LayoutHeader\" colspan=\"2\">");

        // Adds a header container.
        AddHeaderContainer();

        Append("</td></tr>");
    }

    Append("<tr><td>");
}

I don't understand why we have if(PortalContext.IsDesignMode(this.ViewMode)). Didn't we just ensure that all that Append methodes will fire only in designe mode when we wrote if(IsDesign) at the begining?