It seems this method has a security level different from the getStaticProperties method.
If you make two classes A and B looking like
<?php
class A{
        protected static $static_var='foo';
        public function getStatic(){
           $class=new ReflectionClass($this);
           return $class->getStaticPropertyValue('static_var');
        }
        public function getStatic2(){
            $class=new ReflectionClass($this);
            $staticProps=$class->getStaticProperties();
            return $staticProps['static_var'];
        }
        public function __construct(){
              echo $this->getStatic2();
              echo $this->getStatic();
        }
}
class B extends A{
        protected static $static_var='foo2';
}
?>
Then the output will be an exception for the getStatic() call, when the getStatic2() will correctly return 'foo2';