How to update the structure of custom table in WordPress?

I'm following this article on WordPress Codex. It says:

You will need to add the following lines to the end of your jal_install function, to check the version and upgrade if necessary:

So, finally the jal_install() function will like this:

function jal_install() {
    global $wpdb;
    global $jal_db_version;

    $table_name = $wpdb->prefix . 'liveshoutbox';

    $charset_collate = $wpdb->get_charset_collate();

    $sql = "CREATE TABLE $table_name (
        id mediumint(9) NOT NULL AUTO_INCREMENT,
        time datetime DEFAULT '0000-00-00 00:00:00' NOT NULL,
        name tinytext NOT NULL,
        text text NOT NULL,
        url varchar(55) DEFAULT '' NOT NULL,
        UNIQUE KEY id (id)
    ) $charset_collate;";

    require_once ABSPATH . 'wp-admin/includes/upgrade.php';
    dbDelta( $sql );

    add_option( 'jal_db_version', $jal_db_version );

    // ------ update table --------

    global $wpdb;
    $installed_ver = get_option( "jal_db_version" );

    if ( $installed_ver != $jal_db_version ) {

        $table_name = $wpdb->prefix . 'liveshoutbox';

        $sql = "CREATE TABLE $table_name (
            id mediumint(9) NOT NULL AUTO_INCREMENT,
            time datetime DEFAULT '0000-00-00 00:00:00' NOT NULL,
            name tinytext NOT NULL,
            text text NOT NULL,
            url varchar(100) DEFAULT '' NOT NULL,
            UNIQUE KEY id (id)
        );";

        require_once ABSPATH . 'wp-admin/includes/upgrade.php';
        dbDelta( $sql );

        update_option( "jal_db_version", $jal_db_version );
    }
}

Obviously, most of the two parts of logic is duplicated. I think that the first part of codes is enough to update the structures, because the dbDelta() will check and update the table.

Do I misunderstand something in this article?