I don't see why they would do that long-term - making all of their posts available somewhere where they can't place advertisements and then NOT federating any of the other place's posts to their own platform in return is MASSIVELY counterproductive from a business standpoint. It would be making the Fediverse the more attractive option solely from a network effect standpoint, and I'm sure Zuckerberg of all people realizes that.
Threads is likely just putting the finishing touches on whatever method of moderating ActivityPub posts they've cobbled together but wanted to test the Threads->AP federation in the meantime.
And speaking of, how do I get the Mosseri account to show up on Nicecrew? 🤔