If you read even a little ways in, that’s clearly not what they’re saying:

Contrary to Republicans’ portrayals, there is no overarching antifa organization or official network. The terms “antifa” and “anti-fascist,” though, do reflect an actually existing world of activists, researchers, thinkers, and organizers at real risk of persecution and dedicated to a specific politics.

You can take it from me: I have organized and raised funds for the real-world structures that make up the anti-fascist movement.