Delete defaultValue validation_groups

I use my RegitrationForm for 2 cases Registration and Edition

so i have a closure in my validation_groups of my RegistrationForm like this : 
```
$resolver->setDefaults(array(
	'validation_groups' => function(Form\FormInterface $form) {
		$user = $form->getData();
		if ($user->getId()) {
			return array('Edit');
		} else {
			return array('Registration');
		}
	}
));
```
The validation_groups of my configuration override my validation_groups of my RegistrationFormType and if i delete the validation_groups of my config.yml the default value are set

The PUGXFormFactory override the FormType validation_groups in createForm method like this : 
```
 public function createForm()
    {
        $type = $this->userDiscriminator->getFormType($this->type);
        $name = $this->userDiscriminator->getFormName($this->type);
        $validationGroups = $this->userDiscriminator->getFormValidationGroups($this->type);
   		
        if (array_key_exists($name, $this->forms)) {
            return $this->forms[$name];
        }

        $form = $this->formFactory->createNamed(
                $name, 
                $type, 
                null, 
                array('validation_groups' => $validationGroups));
        
        $this->forms[$name] = $form;
        
        return $form;
    }
```

why override the validation_groups in FormFactory?  why not keep the validation that already exist in Formtype?