This feature was removed in revision 1.38 of xml2html.xsl. It is useful if the nested component has documentation (in addition to the documentation for the type of the nested element). For example, a nested optional or multiple occurrence element may have documentation describing the conditions that cause the element to be present and/or how many elements to expect. Or, a type may be used for multiple roles, and the role documentation would logically go with the nested component.
I understand why this feature was removed. I recommend generating the component detail only if one or more doc:element/doc:documentation elements are found. The presence of these elements would indicate that the author has component-specific documentation.