I think that if I were a whistleblower, I would have no interest in taking my brown envelope to a media organization with a paywall.
This is a down-side to paywalls that’s probably worth talking about. Whistleblowers want exposure. Paywall systems don’t provide that. Rather than getting the news out to everybody, the whistleblower who goes to a newspaper with a paywalled site gets the news out only to subscribers.
When your goal is to blow the lid off some scandal, you go the the paper with the biggest potential audience. Paywalled sites don’t provide that.