The showDetailHeader provides a means of toggling the contents under a header between being disclosed(shown) or undisclosed(hidden).
On mobile devices the showDetailHeader renders nothing itself, but does render its children.
If the "disclosed" property on the showDetailHeader is set to false, the icon arrow will point sideways, and the children of the showDetailHeader will not be rendered. If the "disclosed" property of the showDetailHeader is set to true, the icon arrow will point down and the children of the showDetailHeader will be rendered.