It's still a positive predictor in general. It just means that, beyond a certain point, it's a negative predictor. Just like a GPA of 3.5+ is probably positively correlated with getting tenure, but maybe getting 4.0 is worse than getting 3.9. Watch the actual video to get the real take away: I think what it meant was that, everybody who gets hired at Google is pretty good. If I just had to pick someone off the street…
I don't think that should take away from the argument of the article, however: programming contest winners are used to cranking solutions out fast and that you performed better at the job if you were more reflective and went slowly and made sure things were right. The idea that a programmer can be very good at one level and have that goodness fail at other levels is important to consider. It is important to consider…
The author of this article appears to think that he or she has provided evidence for the sentence you quoted, but a number of comments in this thread have pointed out that isn't what the evidence says; so the quoted sentence is simply speculation.