wp_editor textarea value not updating

I am using the *_add_form_fields action to add fields to the edit/add term page. One of those fields is a wp_editor().

The problem I am facing is that when I output the WordPress editor on the page like so:

wp_editor('test', 'mydescription', array('textarea_name' => 'my_description'));

and then if I click in the editor on the page and change the default value from test to something else the $_POST['my_description'] variable is still set to test

Should I be adding an additional setting to my editor? Is there a reason why I cannot change the value of the textarea?

Below is a simple test case that shows this. You can paste this code at the top of twentyeleven/functions.php in a default install of
WordPress. Then visit the add tag page and try to add a tag. You will notice that the posted value for my_description will not change…

class Test{

	function __construct() {

		add_action('add_tag_form_fields', array($this, 'add_tag_form_fields'));
		add_action('created_term', array($this, 'created_term'));
	}

	function add_tag_form_fields($tag){

		if ( current_user_can( 'publish_posts' ) ):

			wp_editor('test', 'mydescription', array('textarea_name' => 'my_description'));

		endif;
	}

	function created_term($tag){
		echo '<pre>';
		print_r($_POST);
		echo '</pre>';
		die();
	}
}
new Test();