singular_name label in custom post type

Question

I was looking to get more info about 'singular_name' label and came across this link. Based on that link 'singular_name' value should show up when I click 'Add New' and 'Add New Post' window appears. My understanding the value would replace the 'Post' part in the 'Add New Post' title. It's not working for me.

My code

function portfolio_register() {

      $labels = array (
        'name' => __('Portfolio'),
        'singular_name' => __('Project'),
      ); 

      $args = array(

            'labels' => $labels,
            'public' => true,
            'show_ui'=> true,
            'capability_type' => 'post',
            'hierarchical' => false,
            'rewrite' => true,
            'supports' => array('title', 'editor', 'thumbnail') 
          );

          register_post_type('portfolio', $args);

    }

    add_action ('init', 'portfolio_register');

I was able to achive the desired effect using 'add_new' and 'add_new_item' labels, however, was just curious what is the purpose of 'singular_name' label.

Answer 1

The answer at that link is incorrect.

The "Edit Animals" text from their answer uses the edit_item label, not singular_name. There's a much longer list of labels that you'll need to provide when registering a post type than just those two. The full list is kept here.

As for singular_name, as far as I can tell, this is only used to label menu items and link suggestions:

In both those examples "Page" is where the singular_name is used.