The Facebook hatred is understandable and justified, but defederating with Threads is a misguided idea:
Federation is not required for them to be able to pull the data. Even if you block an instance, they can still pull whatever they want.
By closing down with Threads, you’ll be basically guaranteeing that that all the millions of people that are there will never be able to migrate away.
By getting major (current) instances to defederate with Threads, it gets easier for Threads to just say “hey, we tried to be open but they still rejected us, so we are just going to go back to our walled garden.”