Someone in Equifax was made aware of the breach on July 29, 2017. It defies common sense that the chief officers of the company did not learn of it until the same time as the general public, over a month later.
I don't believe there's any claim that they didn't learn of it until the public announcement, only that they didn't know of it at the time of the stock sale which was on Aug 1st, only a few days after the breach was "discovered".
Now, based on my experience, it's entirely possible that the July 29th "discovery" date only refers to the date on which some security analyst noticed abnormal behavior. That, combined with the possibility that Equifax doesn't have good security communication practices in place, it easily could have been a few days (or even weeks) before the security team looked into it enough to know the size of the breach and escalated it up to the C-suite.
