RTWs seem to be an exception to this. I've put plenty of random codeshares on my tickets that aren't related to my inbound flights and / or a connection with the codeshare carrier I'm using. I quite intentionally try to set them up to have as near zero AA, BA, and IB codes as possible, so do a lot of work looking for more advantageous codeshares to replace those where needed. I will certainly continue to do so until / unless AA reverses course and treats RTWs as Special Fares again. If they are treated as Special Fares again then they aren't nearly so punative on AA codes.