Edit tags page for hierarchical taxonomy doesn’t show taxonomies at all depths

I created a taxonomy called “portfolio categories” for my portfolio custom post type. They’re hierarchical and supposed to be behave like categories. when i’m editing a single portfolio post… i have a metabox where i can assign the proper portfolio category. It shows all categories at all the depths.

but when i am on the Taxonomy page (edit-tags.php?taxonomy=portfolio-cats&post_type=portfolio) then it only shows top level categories and their immediate children… and no further. so grandchild-level categories are missing even though there are portfolio pieces assigned to them.

is this default behavior? b/c i can see unlimited depths on the regular Categories page. should a hierarchical taxonomy behave the same?

/*
 * Builds the a tag taxonomies
 */

function create_portfolio_taxonomies() {
// Add new taxonomy, make it hierarchical (like categories)
  $labels = array(
    'name' => _x( 'Portfolio Categories', 'taxonomy general name' ),
    'singular_name' => _x( 'Portfolio Category', 'taxonomy singular name' ),
    'search_items' =>  __( 'Search Portfolio Categories' ),
    'all_items' => __( 'All Portfolio Categories' ),
    'parent_item' => __( 'Parent Portfolio Category' ),
    'parent_item_colon' => __( 'Parent Portfolio Category:' ),
    'edit_item' => __( 'Edit Portfolio Category' ), 
    'update_item' => __( 'Update Portfolio Category' ),
    'add_new_item' => __( 'Add New Portfolio Category' ),
    'new_item_name' => __( 'New Portfolio Category Name' ),
    'menu_name' => __( 'Portfolio Categories' ),
  );    

    register_taxonomy( 'portfolio-cats', array('portfolio'), 
        array( 
            'hierarchical' => true, 
            'labels' => $labels, 
            'rewrite' => array( 'slug' => 'portfolio','with_front' => true, 'hierarchical' => true  ),
        ) );

    //preset some categories
    my_add_term($postID,'portfolio-cats','Print');  
    my_add_term($postID,'portfolio-cats','Digital');

}
add_action( 'init', 'create_portfolio_taxonomies', 0 );



function my_add_term($id, $tax, $term) {

    $term_id = intval(term_exists($term));
    if (!$term_id) {
        $term_id = wp_insert_term($term, $tax);
        $term_id = $term_id['term_id'];
    }
    $result =  wp_set_object_terms($id, array($term_id), $tax, FALSE);

    return $result;
}