I don’t know. I would like to subscribe to someone on Threads from Mastodon (since both are Twitter alternatives), if they don’t have Mastodon account (which let’s be honest they probably don’t). Zuck does not get any of my data (besides what’s available publicly anyway). If Threads decides to go full EEE, I’ll stop getting updates from people on Threads, same as I don’t get updates from people on IG right now. I think proliferation of ActivityPub protocol would be the greatest advantage.
Moreover, I think we should follow the email architecture - I might use i.e. Proton Mail, but it does not prevent me from sending emails to Gmail, which I think is a bad provider, who collects a lot of user data. In fact if Proton Mail forbade sending email to Gmail I would be really displeased about that.
The goal is to allow people to choose where they want to go and ActivityPub is what can help with that, unlike blocking Threads.