Wordpress 3.2.1 noheader bug demo

<?php
/*
Plugin Name: Demonstration of noheader bug
Plugin URI:
Description: Demonstration of noheader bug
*/

add_action('admin_menu', 'test_admin_menus');

function test_admin_menus() {
    $pluginPage = add_options_page('noheader test', 'noheader test', 'manage_options', 'noheader-test', 'test_display');
    add_action('admin_head-'.$pluginPage,'test_admin_head');

}

function test_admin_head() {
    //create a global var, so we know if run
    global $test_variable_to_test;
    $test_variable_to_test = 'PHP included!';
}

function test_display() {
    if ($_GET['noheader']) {require_once(ABSPATH.'wp-admin/admin-header.php');} //include the header if not included by WP

    global $test_variable_to_test;

    echo '<p>$test_variable_to_test was set to: <strong>'.$test_variable_to_test.'</strong></p>';

    echo '<form method="POST" action="'.get_bloginfo('url').'/wp-admin/options-general.php?page='.$_GET['page'].'&noheader=1">';
    echo '<p>Submit this form to see the $test_variable_to_test variable disapper</p>';
    echo '<input type="submit" />';
    echo '</form>';
}