Did you read the example? The point is coordinating (and negotiating) with friends-of-friends, when your friends expect to bring said friends-of-friends, without requiring your friends act as a proxy.
> MMS group or Signal group
I don’t see these as fundamentally different from a Facebook event; the point, in my mind, was to compare the class of digital ephemeral forums from the coordination strategies possible when you don’t have any such digital ephemeral forum available.
However, Facebook events have the advantage over MMSes, at least, of people who join/are invited into the event being able to see the history of the conversation so far.
Facebook went in the rubbish along with High School for me, its been years since I last logged in. I doubt that cesspool will see me anytime soon.