Playing with TemplateController, i saw in the documentation https://symfony.com/doc/master/templates.html#rendering-a-template-directly-from-a-route that i may send extra arguments

In fact, those extra arguments seems not managed by the TemplateController following the source code https://github.com/symfony/symfony/blob/5.0/src/Symfony/Bundle/FrameworkBundle/Controller/TemplateController.php (same for 4.*)

Maybe the documentation is not enough explicit about what those extra arguments are used byt Symfony, if they are.