I was referring to Bridgy, not Bluesky, regarding privacy. It acts like a middleman between whatever you're using and Bluesky. And it isn't really opt-in in that sense, because the majority of users would not even be aware of this even existing. An opt-in feature would be directly implemented into a platform, like a toggle you could switch within your account settings. Whether that is opt-in or opt-out is personal preference I guess, but with that logic it should be ideally the same for all native instances as well.