using ``new \Twig_Function_Method($this, 'renderer->renderCsrfToken'),`` was optimizing performance by avoiding a function call on the extension. Using a callable outside the extension like ``array($this->renderer, 'renderCsrfToken')`` on the other hand is less performant than using a method on the extension, because Twig cannot optimize the compilation of the method and will need to load all extensions to ensure that the callable is registered in the Twig environment when rendering the template (which is not the case when using PHP functions or methods on the extension itself).