This is not true.
The App view, relay, PDS, and mobile app, code is all open source. Anyone can spin up their own version if they want.
If you want a complete copy of bluesky (reflecting the bluesky post firehose) it’s prohibitively expensive, but you can spin up your own version if you want.
The only thing that’s missing is bluesky federating anything other than PDSes by default, but you can 100% go in the other direction.
A good overview is here: What bluesky is and what bluesky is not
More than likely we’ll see in/outbox functionality similar to activitypub, so the PDSes could interop with ActivityPub and individually talk to one another