<authorgroup><author><orgname> not displayed on the title page for PDF

Using stylesheet v1.75.1, the <orgname> is not displayed on the title  
pages in PDF documents.  It is in HTML document.


<?xml version="1.0" encoding="UTF-8"?>
<book
	xmlns="http://docbook.org/ns/docbook"
	xmlns:xi="http://www.w3.org/2001/XInclude"version="5.0">
	
	<info>
		<title>Title Test Docbook Document</title>
		<subtitle>Displing &lt;authorgroup&gt;&lt;author&gt;&lt;orgname&gt;
		 Element on the Title Page</subtitle>
		<authorgroup>
			<author>
			   <orgname>ACME Corp.</orgname>
			</author>
		</authorgroup>
	</info>
	<chapter>
		<title>Empty Chapter</title>
		<para/>
	</chapter>
</book>

Is this a bug in the PDF stylesheet?

Paul Spencer