PHP Phalcon Routing with file extension

In my PHP Phalcon 3 Application I have a custom route:

$router->add("/{chapter}/{name}.{type:[a-z]+}", array(
        "controller" => 'images',
        "action" => 'getFile',
    ));

I test the application local with PHP Builtin Server, other routes are working regulary. If i test the route above: http://localhost:8000/XYZ/test.jpg I always get a 404. But in regards to the documentation it should work: https://docs.phalconphp.com/en/latest/reference/routing.html

Do you have any idea whats wrong?

This is my .htrouter for the php built in server:

<?php

if (!file_exists(__DIR__ . '/' . $_SERVER['REQUEST_URI'])) {
    $_GET['_url'] = $_SERVER['REQUEST_URI'];
}
return false;