adding parameters to overridden method E_STRICT observation

It appears (PHP 5.3) that if you are overriding a class method, it is okay to you can add additional parameters, as long as they have default values.

For example, consider the class:

class test1 {
  public function stuff() {
    echo "Hi";
  }
}

The following class extends "test1" and will produce an E_STRICT warning.

class test2 extends test1 {
  public function stuff($name) {
    echo "Hi $name";
  }
}

But, the following does not produce an E_STRICT warning.

class test3 extends test1 {
  public function stuff($name = "") {
    echo "Hi $name";
  }
}

While class "test3" doesn't produce an E_STRICT warning, I have been under the impression that PHP does not allow method signatures to be overloaded overridden. So, I have to ask. Is my observation a bug/flaw or actually correct intended behavior?

Further, if a default argument parameter is okay, why is a non-default argument parameter not okay?