Plenty of posts recently questioning whether BlueSky is actually a decentralised, federated social network like the Fediverse.
(Yes, the following description of ATproto is a gross oversimplification. I realise this. Bear with me a moment.)
Basically, under BlueSky's AT Protocol, you can opt to have your data hosted on your own personal data server (PDS). But these servers all need to connect to a central relay, and at present the only central relay is BlueSky.
Any account that follows Bridgy Fed @bsky.brid.gy also gets federated into the Fedi.
Now.
Let me introduce you to WhiteWind. https://whtwnd.com/
What's WhiteWind?
It's a longform blogging platform, where all your blog posts are saved to your BlueSky PDS.
So right now, today, you can set up your own PDS. Allow BSky access and store your BSky posts in it. And also grant WhiteWind access and allow WhiteWind to store its files there.
And any BlueSky posts replying to your WhiteWind blogs are visible — on WhiteWind.
So potentially, in the future, you could be storing data from multiple social networks and apps — including photos and videos — in your PDS.
In effect, federating across multiple networks doesn't happen at the level of BlueSky. It happens at the level of your account.