I think this was a misunderstanding of a bit of shitty functionality in threads. If you had Instagram and made a linked threads account, you would see follow suggestions for people who hadn’t made an account yet. It was basically “if this person makes a threads account I want to be following them”. I don’t believe it meant those suggested people had a shadow account or anything like that though. Still sketchy and probably drove inorganic growth, but I believe the number of users is counting the number of people opting into opening an account.

It’s just naturally going to be incredibly high, because so many people use Instagram and would’ve been exposed.