The standard claim in bystander effect research is that an individual bystander's probability of intervening goes down as the number of bystanders increases (see, e.g., Wikipedia). Whereas this study looked at the probability of any intervention from the group of bystanders, which is a different thing.
The abstract of the paper actually begins with this distinction:
Half a century of research on bystander behavior concludes that individuals are less likely to intervene during an emergency when in the presence of others than when alone. By contrast, little is known regarding the aggregated likelihood that at least someone present at an emergency will do something to help.
So: not a debunking. And another example of why it's good practice to check the paper in question (or at least its abstract) and the Wikipedia article(s) on the topic rather than believing news headlines.