I never claimed the war was not already over due to Sherman, however, Lee's hypothetical leadership of the Army of the Potomac has very little to do with the fact USG tactically defeated him in the Overland Campaign. They most major engagements until Lee met Grant, and the better general won. Based on what I've read about Overland, it wouldn't have mattered if Lee was on equal footing, he was consistently outmatched by Grant.