I'd posit that even if they already voted, people are still checking the news to see if there is late breaking news that will affect the broader opinion, even if they "know" that it won't affect theirs.
Anyway, my broader point is that Greenwald, and likely many others, feel immense pressure to get this out before the election, so that people have "all the relevant information", but the truth is, we never have all the relevant information because information exists in a continuum not a binary space.
The news media is. The public (especially, given the pace of early voting, this year) doesn't seem to be, as much.