Is there any public third party BlueSky storage server yet? Last time I tried setting up an account there it only showed the main instance despite all the fuss about decentralization. Or am I grossly misunderstanding how different it is from the fediverse?
As far as I know, there aren't any yet. Even if there were, I personally wouldn't trust them for the same reason I wouldn't use any Mastodon instance besides mastodon.social: if the PDS shuts down abruptly, your account is gone forever.
Bluesky and ATProto are designed specifically to hide the ways in which it's decentralized.
Well, that diagram brings up an interesting point. In fediverse if the host dies the federated content can still live on (theoretically, I haven't checked to see if they cull content from dead hosts) but ATProto would dictate that the host is missing and therefore all content associated with the host is now immediately 404.