It's no secret that Hersh's work has become increasingly suspect in recent years. Every time he writes, he cites a single anonymous source and yet manages to go into an implausible level of detail and completeness with neatly tied up loose ends you'd only expect to find in a Tom Clancy novel. The only reason this story has been rescued from the dustbin is due to Hersh's (old) reputation, which though well earned, shouldn't just give him a pass.
https://www.businessinsider.com/robert-grenier-reflects-on-s...
https://www.vox.com/2015/12/21/10634002/seymour-hersh-syria-...
He had a lock on the genre like nobody else before or since.