This view of it will assist hackers in getting a head start before the auto update cycle gets to your device and you're notified. And if you're hit but something like this before that, your iPhone will no longer be able to update and apply the fix.
Of course, there's no way to find an objectively "correct" time frame since update cycles vary, but a month or two ought to give plenty of time for the updates to roll out and users to be made aware.
Alternatively, they could publish the gist of the exploit without providing enough detail to actually perform the exploit.
The bad guys (many enough of them) will anyway figure it out right away after the patches have been published, because with every patch, people will (and should) ask "why".