It's open as in "diverse" imo. Blue sky is still mostly white, mostly western, mostly technical people. X on the other hand has so many different communities and is much more open for "average users". It's a similar problem on mastodon
However, this is exactly the argument that people use to criticize bluesky. What is an echo chamber if not going to a place where you get the content you want. 99% of people who think they're taking a principled stand on moderation or openness in either direction are lying to themselves.