The experiment was to turn off social media, not turn off their phones.
You can still get news directly from news sources, rather than indirectly from social media, which is not generally the primary source of news.
"In a randomized experiment, we find that deactivating Facebook for the four weeks before the 2018 US midterm election...
...(ii) reduced both factual news knowledge and political polarization;"
[1]: https://www.aeaweb.org/articles?id=10.1257/aer.20190658
2) How likely is activism to come from people who are only connected to the outside world via Facebook?
3) Reduced "factual news knowledge" is not the same as "didn't know about the Roe verdict". I was somehow aware of the verdict without being on Facebook. It's hard to tell from just the abstract, but we don't know how they define "factual news knowledge". In my opinion, most so-called "news" is just trivia and unimportant. Politician A said X, politician B said not-X, blah blah, ad nauseam. IMO it's actually better to take a step back from the daily trivia and look at the broad historical perspective. Better to read a book than a headline. A person can become "too informed" about things that don't matter, missing the forest for the trees.