They didn't source it, I see no mention on Crunchyroll or the official website (no mention of even Japanese streaming never mind WW) so unless Anime Now got the scoop and hid it at the bottom of an article it's not any more confirmed than it was yesterday.
I would at count them as a credible source considering who owns Anime Now:
As a part of Anime Consortium Japan, a subsidiary Bandai Namco Holdings, we have a level of access to today’s anime that is simply unparalleled.
oh didn't look into that. Just had a quick glance at their articles to see if they've posted any "Tokyo Ghoul 3 confirmed for August 23 2017" style posts.