ArrayHydrator and ObjectHydrator return different result sets for the same query

CREATE TABLE IF NOT EXISTS `specification_value_test` (
  `specification_value_id` int(11) NOT NULL AUTO_INCREMENT,
  PRIMARY KEY (`specification_value_id`)
) ENGINE=InnoDB  DEFAULT CHARSET=latin1 AUTO_INCREMENT=96058 ;

INSERT INTO `specification_value_test` (`specification_value_id`) VALUES
(94506),
(94526),
(94564),
(94589),
(94593),
(94606),
(94607),
(94609),
(94711),
(94712),
(94780);


CREATE TABLE IF NOT EXISTS `variant_specification_value_test` (
  `variant_id` int(11) NOT NULL,
  `specification_value_id` int(11) NOT NULL,
  PRIMARY KEY (`variant_id`,`specification_value_id`),
  KEY `specification_value_id` (`specification_value_id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

INSERT INTO `variant_specification_value_test` (`variant_id`, `specification_value_id`) VALUES
(545208, 94506),
(545209, 94506),
(545208, 94526),
(545209, 94526),
(545208, 94564),
(545209, 94564),
(545209, 94589),
(545209, 94593),
(545208, 94606),
(545209, 94606),
(545208, 94607),
(545209, 94607),
(545208, 94609),
(545209, 94609),
(545208, 94711),
(545208, 94712),
(545208, 94780),
(545209, 94780);

CREATE TABLE IF NOT EXISTS `variant_test` (
  `variant_id` int(11) NOT NULL AUTO_INCREMENT,
  PRIMARY KEY (`variant_id`)
) ENGINE=InnoDB  DEFAULT CHARSET=latin1 ROW_FORMAT=COMPACT AUTO_INCREMENT=545210 ;

INSERT INTO `variant_test` (`variant_id`) VALUES
(545208),
(545209);

/**
 * @Table(name="variant_test")
 * @Entity
 */
class Variant extends Base
{
    /**
     * @Column(name="variant_id", type="integer")
     * @Id
     * @GeneratedValue(strategy="AUTO")
     */
    protected $variantId;
    
    /**
     * @ManyToMany(targetEntity="SpecificationValue", inversedBy="Variants")
     * @JoinTable(name="variant_specification_value_test",
     *   joinColumns={
     *     @JoinColumn(name="variant_id", referencedColumnName="variant_id")
     *   },
     *   inverseJoinColumns={
     *     @JoinColumn(name="specification_value_id", referencedColumnName="specification_value_id")
     *   }
     * )
     */
    protected $SpecificationValues;
}

/**
 * @Table(name="specification_value_test")
 * @Entity
 */
class SpecificationValue
{
    /**
     * @Column(name="specification_value_id", type="integer")
     * @Id
     * @GeneratedValue(strategy="AUTO")
     */
    protected $specificationValueId;
    
    /**
     * @var Variant
     *
     * @ManyToMany(targetEntity="Variant", mappedBy="SpecificationValues")
     */
    protected $Variants;
}



$result = $em->createQueryBuilder()
    ->select('Variant, SpecificationValue')
    ->from('Variant', 'Variant')
    ->leftJoin('Variant.SpecificationValues', 'SpecificationValue')
    ->getQuery()
    ->getResult();
	
// returns 9 specification values for first variant and 7 specification values for second variant
\Doctrine\Common\Util\Debug($result, 4);

$em->createQueryBuilder()
    ->select('Variant, SpecificationValue')
    ->from('Variant', 'Variant')
    ->leftJoin('Variant.SpecificationValues', 'SpecificationValue')
    ->getQuery()
    ->getArrayResult();

// returns 9 specification values for first variant and 9 specification values for second variant
\Doctrine\Common\Util\Debug($result);