But a broken clock is right twice a day and a bad journalist can break two big stories in a career of publishing lies.
If you publish all at once, others can go and verify the details. The source is protected.
If you verify pre-publication, e.g., go to the diving school in Florida and ask too many questions, you (and the source) will be under surveillance in no time.
https://slate.com/news-and-politics/2015/05/seymour-hershs-u...
There are plenty of powerful people trying to discredit reporters who tell who tell the truth, so we should also be skeptical of attacks on Hersh.