“Cars without issues repaired under warranty don't need to be reported to the NHTSA – National Highway Traffic Safety Administration. After all, warranty repairs are due to manufacturing issues and are, therefore, an OEM's responsibility. Goodwill fixes are something automakers do to please their clients.”

Seems like if they classify a repair as goodwill they can avoid a car receiving a lemon designation. There’s also a link to an article that alleges Tesla classifies warranty expenses as goodwill in order to lower their warranty accruals per vehicle, boosting profit margins.