Greenberg tweets: "system failed miserably"

The last part is the most telling. What exactly did Adam Schefter say that convinced him that the process was unfair and failed miserably?

I bet it was Schefter saying that the league told him this was it in terms of evidence. There was always the opening of "well, they HAVE to have more than this, they don't HAVE to show everything now," and it's gone with Schefter saying the NFL told him there wasn't anything else.