Hersh's story is ridiculed for a reason, it relies on a single unidentified source. I.e. he could have literally made it all up, or, that source could be an intelligence agent for who knows what country, or just some guy on an ego trip, or it could be legitimate, but there's no evidence anywhere else that corroborates any part of his story. Good journalists usually corroborate a source's story rather than publishing it on blind faith.