I didn't want to alter the original too much, but you're correct.
```Use this to extend the base default behavior.``` is good.

But until https://github.com/symfony/symfony/issues/5432 is fixed that whole comment doesn't make sense anyway because that class can't simply be extended and provided as ```success_handler``` option, because the base options won't be set and the extending class won't have any information on where to redirect to etc.

But apart from that I'm fine with your suggestion.