@Scofisticated Ahh! Well, the way I understand it is, if your post is duplicated there and they run a generic/all-public-posts to data mine, then yes. Since the way AP works is to create a pseudo-profile in each instance your account was seen/followed, and thus your posts/replies from that point on, then you exist in that instance.
However, if they'll only run such for local accounts (if ever they do data mining), then all we have is trust. In the same way that we trust the other instances our followers are on.
For example, I now have a pseudo-profile in your instance with some of my posts/replies recorded there. I can only trust your instance admin and host from hereon. In the same way that you do for our instance. It's similar with Threads, they're technically an "instance", who happens to have more funds and is a corporation.
But, if we think about it, it's the same with others like Wordpress, Flipboard, Ghost, and other big companies. Like any other instances, we can only trust that they won't do something or are not doing something for federatid content (since we're technically not their users/customers). (I'm not saying they are or they will, just examples.)
At least that's how I see it. 🙂