There’s nothing stopping attackers from manipulating the data they make public.
It’s one thing to have all of your dirty laundry aired in public for everyone to see. It’s another thing entirely for someone to throw in a few choice items that aren’t real.
Imagine trying to explain to the press, eager to publish the worst of the details in the documents, that everything is accurate except this particular email. Or that particular memo. That the salary document is correct except that one entry. Or that the secret customer list posted up on WikiLeaks is correct except that there’s one inaccurate addition. It would be impossible. Who would believe you? No one. And you couldn’t prove it.