The account that posted it, [email protected], is listed[1] as the "owner" of Project Zero, which implies to me that they may be a user account, but quite likely one that has a script running under its permissions.
There certainly could be a human-controlled kill-switch to this release process, of course, and it's possible that "hawkes" manually goes through a list of vulnerabilities every day and clicks "release".
[0] http://www.convertunits.com/dates/90/daysfrom/Nov+25,+2016 [1] https://bugs.chromium.org/u/1279493906/
The one who didn't expect it to miss the deadline is the same as the person who originally reported the vulnerability. It is therefore a safe assumption that this person understands the disclosure process involved.
Furthermore it is a safe bet that the bug is exploitable. I'm sure that the black market will shortly have people using it.