This web page gives you the overview, and refers you back to the original scientific paper.
Don’t you believe it.
Our grid might be so unreliable that there’s no way to predict how an attack will affect it. Chances are, there are places where attacking the grid would have spectacular, hard-to-explain results. If it’s unreliable, how can scientists demonstrate what an attack won’t do to it? After all, electrical loading accidents in the past have produced dramatic, unexpected results.
But I think we can be happy that no analytical person can determine a good place to knock the grid over like so many dominoes. That’s good news.