This story is over 10 yrs old and even back in '04, people in and out of the journalism profession had their doubts on what Hersh claimed to have seen and even about Hersh himself.
Sy Hersh's Loose Relationship With the Literal Truth
Sy Hersh's Loose Relationship With the Literal Truth
Basically, Hersh have a history of avoiding putting in print what he cannot prove or confirm what was said, and when he does say something about an event, he have a history of omission of critical details and even changing vital elements like dates and names, rendering the story unverifiable.
About this claim by Hersh, if one chose to believe him, in the absence of anything concrete in print, belief of Hersh depends more on one's own attitude about US and far less about facts and their veracity.