Salon said that he was in the same prison at the same time, and could well have been through the same torture. But his wasn't photographed.

In fact I'd think that was fairly likely - when a group gets the idea that doing X to prisoners is a good idea, they are likely to do X to a whole bunch of them.

It is a short step from that to his thinking that he was the one pictured. Given how memory works, any small discrepancies by which he might have eventually realized that that wasn't true would be erased from his mind.

Therefore even though he wasn't the one photographed, I'm not inclined to doubt his sincerity.

Cheers,
Ben