Once more I remind you, the REPORT is NOT EVIDENCE. The CHP officer can only testify as to what his investigation revealed (measurements, physical evidence, etc.) and, to a lesser extent, what he was told (subject to hearsay). You can bring the driver swap up at trial IF it goes to trial, but, that doesn't change the fact that you appear to have fled the scene without providing the required information in violation of VC 20002 (or VC 20001 if a felony). Who drove and whether they were licensed or not would NOT absolve you of guilt for fleeing.
Your attorney isn't dealing with a defense strategy at the moment because there is no prosecution or defense at this point. Adding information and statements might only hurt you! Adding a supplement where you run off at the mouth may well hang you in a hit and run case, so he's probably wanting you to keep your shorts on and sit tight and wait and see.