isn’t this missing a crucial detail?
The whole reason why those 100k users can be switched across service providers so easily is because all of their ID keys (did:plc) are stored on the singular Bluesky-operated https://plc.directory
That key-ownership does not change with the move, so complete Bluesky-independence has not happened yet in this case. Those users are still dependent on an essential piece of Bluesky-infrastructure.