No, for at least two aspects. So Malaysia have a codeshare on some NCL-LHR services, but only for those that make sense for connections. BA have many codeshares going into ORD on AA, so long as they arrive around lunch time, for onward connection to LHR. There would not be an obvious point running say ROC (Rochester NY) into ORD late at night. Secondly, being manually controlled frequent changes often muck up the arrangements, either briefly or sometimes for an extended period.