The protocol has a notion of moderation accounts, sometimes called "labelers" because they can apply labels to your account. Users generally [1] subscribe to the moderation that they want to see. They can then set those labels to make the application to "show", "warn" (collapse by default, click to expand), or "hide" based on the labels.
1: People using the bluesky app cannot unsubscribe from the bluesky moderation service, but that is a policy choice of the bluesky app, not a protocol level choice, other clients can do as they choose.
If you register a Bluesky account from Germany, your account is assigned the German moderation labeler with no option to opt out. As soon as I noticed, I created a new account using a US IP address. This fixed it.
While signing up for moderation sounds very attractive to me, Bluesky's whole layered moderation approach seems designed to maximize algorithmic censorship.
Compare that to, for example, a mastodon instance (or a forum like HN) where you participate because you align with the general moderation approach cultivated by and within the community.
Bluesky moderators take down abusive and harmful posts. There is a daily uproar on the left about how they do this to "kiwifarms but leftishly" behavior under the guise of being "anti-trans". If right-wing centered posts are getting taken down, it is because they are abusive and harmful.
Bluesky popularized subscriber lists, like blocklists. A large portion of the network mass-mutes or mass-blocks anyone on the big right-wing block lists. This is user behavior, not the platform censoring right wing people.
(There are a few other far-right mastodon instances, but then there are pockets of the far-right on bsky, too)
When Bluesky was taking traction, the cultural expectation among its audience was already for the platform to heavily shape the narrative. Paradoxically, AFAIK the Bluesky devs themselves are pretty serious about it being an open standard, though I'm basing this on what I heard. So I mostly believe people that the echo chambering you mention is structured in a way that it's technically not centralized. Though in practice, it's way easier to amplify left wing messages on closed websites like YouTube, Facebook, X (I'm basing this on algorithmic recommendations I'm getting and experience of people I know) than the other way around on Bluesky. But this is just the weight distribution of the audience.
Even then non-left supervised Mastodon ecosystem is something of a deep cut. I mean you're right it exists and now I recall hearing about some drama years ago, but not a part of the front and center info about them, for any common person. So I'm not fully buying the contrast you're trying to build here.
Elon Musk took over Twitter and made it rabidly right-wing. As a result, a lot of left-wing people went to Blue Sky.
Social networks are just groups of people: if such a network starts with a core group that leans heavily on a particular end of the political spectrum, the network will also (even with zero bias from the network itself) lean that way.