EntityReferenceSelection Plugin aren't available Field Config form

When creating new EntityReferenceSelection plugins they are not available for selection in the Entity Reference Field settings form. To recreate this bug I did the following:

1. Create a custom plugin using the default selection plugin provided by the core Drupal Entity Component using the following annotation for my plugin definition

/**
 * Custom plugin implementation of the Entity Reference Selection plugin.
 *
 * @EntityReferenceSelection(
 *   id = "news",
 *   label = @Translation("Related News"),
 *   group = "custom",
 *   weight = 0
 * )
 */

2. Added a new field to the Basic Page Content Type
3. Looked for my plugin "Related News" in the "Reference Type" select list

I was expecting to see my plugin in the select list of available EntityReferenceSelection plugins but instead did not. Debugging verified that my plugin was discoverable to the SelectionPluginManager. If I use the the same string for 'id' and 'group' in the plugin definition e.g. 'news' and 'news, and clear the cache it's available as an option from the select list.

I believe the issue is in Drupal\Core\Field\Plugin\Field\FieldType\EntityReferenceItem::fieldSettingsForm; specifically:

    // Get all selection plugins for this entity type.
    $selection_plugins = \Drupal::service('plugin.manager.entity_reference_selection')->getSelectionGroups($this->getSetting('target_type'));
    $handlers_options = array();
    foreach (array_keys($selection_plugins) as $selection_group_id) {
      // We only display base plugins (e.g. 'default', 'views', ...) and not
      // entity type specific plugins (e.g. 'default:node', 'default:user',
      // ...).
      if (array_key_exists($selection_group_id, $selection_plugins[$selection_group_id])) {
        $handlers_options[$selection_group_id] = Html::escape($selection_plugins[$selection_group_id][$selection_group_id]['label']);
      }
      elseif (array_key_exists($selection_group_id . ':' . $this->getSetting('target_type'), $selection_plugins[$selection_group_id])) {
        $selection_group_plugin = $selection_group_id . ':' . $this->getSetting('target_type');
        $handlers_options[$selection_group_plugin] = Html::escape($selection_plugins[$selection_group_id][$selection_group_plugin]['base_plugin_label']);
      }
    }

I don't fully understand what the if statement is checking her. This logic will only add plugins that have identical groups and ids to the select options. I couldn't find any documentation support this. I would think all plugin ids from all groups should be available as options (excluding default:node, default:user which is checked for in the elseif conditional.

This is a simple enough fix that I'd love to do, if someone can elaborate on the intended behavior of these plugin definitions and if my assumptions above are correct.