What about to post exactly the same sentiment. I'm finding it hard to access the full study, but I'm guessing "less knowledgeable about current events" means the treatment group weren't as aware of the various disconnected things the media puts in the faces of their audience and then drops within a week, reducing the events to mere trivialities.
This matches my experience. Reducing my online activity has really made me "miss out" on all the "crazy stuff" happening. Basically it is like if someone took Trump's Twitter account away. It is much more relaxing.
Apparently, they couldn't identify any downsides to quitting Facebook.