> Debatable, this mostly boils down to the client design choices and priorities, and has little to nothing to do with the protocol.

I think it does.

How would you as a client choose that the (potentially) encrypted chat history of all rooms is immediately available after logging in, let alone after joining an encrypted room?

You can't:

- how long messages are stored server side depends on someone else's server

- encrypted messages aren't recoverable from new sessions