It’s not widely shared because the actual facts of that story don’t help the “Facebook will kill activity pub” narrative.
Before Google Talk and Facebook Messenger adopted XMPP it was an extremely niche messaging protocol only used by nerds. After Google Talk and Facebook Messenger dropped XMPP it went back to being a niche messaging protocol used only by nerds.
The standing of XMPP was, if anything, better off after it was abandoned by Google Talk and Facebook Messenger than before those platforms adopted it.
So then for somebody trying to scare monger about Meta, this story doesn’t help. It hurts that narrative, and that’s why people panicing about Threads aren’t talking about XMPP.