The problem is that, since proofs-of-concept have leaked but the patch isn't available, bad guys can attack any site whose operators aren't part of the club, and the only thing the operators can really do to prevent that is to take the site offline. (PHP core team has denied that the configuration change fixes the problem.) I would call this a significantly worse outcome than everyone finding out about the vulnerability at the same time, since in that case operators can take timely action if they get the news quickly enough.