Yeah this is worth talking about a bit. I'll say more about why I consider bluesky to be part of the fediverse. I'm no expert. So this is mostly my way of thinking. I'm not trying to represent any "official" stance. (Again, there's nobody who could do that. Nobody is in charge.)
To me, the thing that makes bluesky count as fediverse is that they intend to support federation and decentralization. They haven't *yet*. But it has always been their stated intent.
https://tenforward.social/@noracodes/111927402077531350