Unexpected result when iterating descendants in node-set using //

ADDITIONAL SYSTEM INFORMATION :
Windows 10 / RedHat OpenJDK 11.0.10 or Oracle JDK 16 2021-03-16

A DESCRIPTION OF THE PROBLEM :
When copying nodes from variable specified in XSLT, that tree fragment has to be converted into the node-set.

<xsl:variable name="tree">
   <entry level="0">
      <entry level="1"/>
   </entry>
</xsl:variable>

However, when using XPath // shortcut for retrieving specific nodes in that tree fragment, I am getting unexpected result. This code <xsl:copy-of select="exsl:node-set($tree)//entry" /> should list two entries, but only that nested one is returned.



STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Run the test case below.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
<a>
   <entry level="0">
      <entry level="1"/>
   </entry>
   <entry level="1"/>
</a>
<b>
   <entry level="0">
      <entry level="1"/>
   </entry>
   <entry level="1"/>
</b>
ACTUAL -
<a>
    <entry level="1"/>
</a>
<b>
    <entry level="0">
        <entry level="1"/>
    </entry>
    <entry level="1"/>
</b>

---------- BEGIN SOURCE ----------
package my.xslt.test;

import java.io.StringReader;
import java.io.StringWriter;
import javax.xml.transform.Templates;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.stream.StreamResult;
import javax.xml.transform.stream.StreamSource;

public class IssueProvider {

    public static void main(String[] args) throws Exception {

        StringBuilder xslt = new StringBuilder();
        xslt.append("<xsl:stylesheet xmlns:xsl='http://www.w3.org/1999/XSL/Transform&#39;");
        xslt.append(" xmlns:exsl='http://exslt.org/common&#39;");
        xslt.append(" exclude-result-prefixes='exsl'");
        xslt.append(" version='1.0'>");
        xslt.append("<xsl:output indent='yes' omit-xml-declaration='yes'/>");
        xslt.append("<xsl:variable name='tree'>");
        xslt.append(" <entry level='0'>");
        xslt.append(" <entry level='1'/>");
        xslt.append(" </entry>");
        xslt.append("</xsl:variable>");
        xslt.append("<xsl:template match='/'>");
        xslt.append(" <a><xsl:copy-of select='exsl:node-set($tree)//entry'/></a>");
        xslt.append(" <b><xsl:copy-of select='exsl:node-set($tree)/descendant::entry'/></b>");
        xslt.append("</xsl:template>");
        xslt.append("</xsl:stylesheet>");

        StringWriter writer = new StringWriter();
        TransformerFactory transformerFactory = TransformerFactory.newInstance();
        Templates templates = transformerFactory.newTemplates(new StreamSource(new StringReader(xslt.toString())));
        Transformer transformer = templates.newTransformer();
        transformer.transform(new StreamSource(new StringReader("<document/>")), new StreamResult(writer));
        System.out.println(writer);
    }
}

---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
Replace //entry with /descendant::entry in XSLT

FREQUENCY : always