It’s not about Zuckerberg, it’s about the userbase. With something that grew to 30 million users literally overnight, it’s impossible to determine what it will be like, and how it will mesh with the existing fediverse content/users.
With something this scale, it only makes sense to secure and observe - pre-emptively block, watch the content, maybe even poll the users on what should be done. There is nothing to be lost this way, it’s only a cautious approach towards a potential later link.
What could be lost is the Threads community overwhelms the lemmy community before there is a chance to react (it is 1000x bigger, after all). It makes sense to be cautious, here.
This isn’t inconveniencing anyone, any user can make an account on Threads as well and use both right now.