This is a really good call out. I've been thinking about this article since I read it earlier today, and I never thought about the distinction between user groups and how people used xmpp vs how people use a activitypub Lemmy/kbin.
I think you are spot on.
Which actually makes me think that mastodon might have a little to worry about since its less anonymous and who you follow actually matters. And there is more interaction between (not anonymous) people.
My friends are like your friends in that we all use reddit, but never even share our usernames with each other.