Correct. Clients can’t tell servers about objects they don’t know about. An object can be created on the server, given to a client, then used as a reference when talking back and forth.
Additionally, replication only goes one way “server->client”. You can’t set member variable A on the client and expect it to just be set on the server. The typical pattern is to call an RPC “ServerSetMyVar(newVal)”, have the server set it there, then make the member variable set to replicate to other clients.
Or you can do “for all clients, ClientDoSomeWork()” inside the server call as well. But that is more heavy handed and also brings in the caveat that the object must exist and be relevant for all the other clients.