What point was that? If you don’t join Threads, they don’t have your data. They do have everything you publish to the Fediverse though, no matter what you do.

They can already harvest the data. Nothing on the ActivityPub is private

How is Threads going to breach your privacy by federating with your instance? How is de federating from Threads going to protect your privacy?

Are you saying hydrogen doesn’t burn because it doesn’t produce carbon?