alt Hacker NewsOn fedi there are several distinct pockets apart from the mastodon crowd which although don't dominate in raw headcount have their own flavour and unique view of the network (in 2nd place is "dark fedi", which has more shitposters, hackers and free speech adjacents; there's also a contingent of Japanese users mostly on Misskey instances). What I get out of AT is that this wouldn't really happen, since the content distribution would dominate your view with Bluesky posts regardless of your relationship with the rest of the network.
In AT you also get communities, in the same way that twitter had weird twitter, black twitter, and so on. But because you, by design, don't really see what PDS people use, it's more fluid.
I personally think that this actually leads to healthier communities but that may be a matter of taste!