That first piston probably created a hot spot on the top part therefore more prone to detonation/melting which happened when they turned the boost up..
Yes, and I don't want to confuse people with this picture as to the current motor problem. I just want to point out that in MMR's "final response" they held up this piston as evidence it wasn't their fault and that it is similar to the current problem. However, they failed to mention that picture number one in their response is the same piston that was struck by the valve and they decided not to replace it.