the issue is that you can have the following file:

```yaml
parameters:
    github.test: true
    github:
        something: foobar
```

This is valid. Using a dot is confusing.

The primary use case for this library was setting the Symfony parameters in the parameters.yml file. In such context, the difference is very important, as the behavior will be

```php
$container->setParameter('github.test', true);
$container->setParameter('github', array('something' => 'foobar'));
```

Having a confusing UI for the configuration is a very bad idea