I wouldn't say that the experiment had no merit at all. After all, military folks go through training to prepare them for possible torture, all while being aware that it's just training.
Of course, that's not to say that such training can ever fully prepare one for being tortured. And although he was able to tap out with his friends and real torturers wouldn't let you, they most likely will stop before you're dead, if they truly want info from you. So keeping that in mind and already knowing what it feels like I would think could potentially prepare someone slightly better for being waterboarded than someone who has no idea what it entails.
Not the best training in the world, but not totally without value.