They just announced a warranty of 8 years and no range restriction retroactively. You also mention that their service is great and the pool is void.
Even if the drive unit has to be replaced before 8 ( or 4 ) years then that is no problem to the customer. It can't be a problem to Tesla or they wouldn't announce this warranty.
The point is if you have replaced the drive unit four times in the first 30k miles (as with the Edmunds car), just how many times are you going to have to replace it once the warranty expires?
Your parent sees extending the warranty as a form of damage-control against this (quite reasonable) fear.
They just announced a warranty of 8 years and no range restriction retroactively. You also mention that their service is great and the pool is void.
Even if the drive unit has to be replaced before 8 ( or 4 ) years then that is no problem to the customer. It can't be a problem to Tesla or they wouldn't announce this warranty.