Wikipedia doesn't use the phrase "group of people", and cites a symposium as a source for the assessment that "it is a highly decentralized array of autonomous groups in the United States," so, I'm not sure this advances the discussion.

It's obvious that the vast, overwhelming majority of people consider themselves anti-fascist. So I really don't think it possible for this term to ever actually describe a particular group of people, excluding other groups of people.

These attempts to shoehorn the word "antifa" into some kind of distinct organization seem like they are just a lingual change to make it more difficult to use this phrase, or more difficult to advance critiques of fascist tendencies wherever they may appear.