The paper found that the vast majority of Twitter users classified as bots were actually human. They analyzed data sets previously used by three organizations responsible for the majority of available papers on the topic.

The authors of the paper concluded that, in the future, any claims that withhold the list of account handles classified as bots should be ignored because the claims can’t be independently verified.

So they didn’t rebuke just one study but datasets underlying most studies on the topic, they analyzed Twitter rather than Reddit, and they did not claim that bots don’t exist. If I am mistaken, someone who’s analyzed the paper in more depth than I did can correct me.