What he was talking about, was the 2 trips. If someone tells their dealer to order the parts, without first checking what was wrong, if that's not what was wrong, who pays for the parts the dealer ordered, but now aren't using. In your case, it's a known issue, and they should actually stock them, but I've seen a few posts where people insisted their MGU was bad, but it turned out to be a belt tensioner. If they don't stock an MGU, but order one because you say it's bad, who pays the money for the part that now sits in the parts department?