Need clarification on check for method views_plugin_display::has_metatags()

metatag_views.module contains the following function, which checks for a method "has_metatags" (which doesn't exist for views_plugin_display):

function metatag_views_views_display_has_metatags(views_plugin_display $display) {
  if (method_exists($display, 'has_metatags')) {
    return $display->has_metatags();
  }
  else {
    return $display->has_path() && $display->uses_breadcrumb();
  }
}

There is a protected method has_metatags() in metatag_views_plugin_display_extender_metatags, which looks like this:

  protected function has_metatags() {
    return metatag_views_views_display_has_metatags($this->display);
  }

I keep wondering: when would views_plugin_display (or a child class) ever implement the method has_metatags()?
Could it be that this is a leftover from an earlier project?