It should be there.  It's instantiated at https://github.com/joomla-framework/view/blob/RendererInterface/src/Renderer/Twig.php#L26 and should be merged with the user supplied config at https://github.com/joomla-framework/view/blob/RendererInterface/src/Renderer/Twig.php#L81

Weird that warnings are being displayed.