JSP :: Page Directive Attribute Session False - Yet Session Created

May be I did not understand the meaning and usage of attribute "session" in page directive. My understanding is if session=false, in page directive, then the JSP page will not participate in the session. However, I have my welcomepage as below:

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
pageEncoding="ISO-8859-1" session="true"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
........
.......
<%= session %>
<c:out value="${pageContext.request.session}"/>

if I choose session=true, then both ways of accessing session works , which means the JSP page participated in the session.

But if I change the session=false, then <%= session %> fails, but <c:out value="${pageContext.request.session}"/> does not fail.

how can c:out still show the session, when session = false