This is misleading, there is no investigation. They just review some additional documents flagged by the public. So the strategy now is to release documents only when their existence can no longer be denied.

If I say I have notes on powerful people and say that empowers me, that’s bragging. Not blackmail, because those people might not even know. If I were to say it to those powerful people, it could be perceived as threatening. But it’s not blackmail, as I don’t demand anything. If I were to use those notes to get something done: that’s blackmail.

The NYT is just reporting what’s ‘fit to print’. Unless there’s verified proof of actual blackmail this description seems apt. Saying you have information on people and you may use it is not blackmail, as that would require a direct request.