This has been an issue for a little bit. The CD cars do not have the same lockup wet clutch set as the regular skyactivs do. They use a more traditional single clutch with a more aggressive material to survive early lockup. Many oems that have tried early lockup with this style of clutch experience significant issues and early wear. GM with the 6L80/90 family are the most notorious for this. The clutch set that turns on going into 4th is a more aggressive friction material that is already high metal content. The iron contaminates that set and is similar to what happens with a brake pad that becomes contaminated and makes a squealing sound.