Re: Not the only ones
It's not only that. They have a legal avenue, too. Since their highly-technical cars require a certain level of craftsmanship to operate properly, they can claim they need to vouch for the replacement parts or they can't vouch for the vehicle's viability (see that outside cars, too, such as with NSF-certified water filtration systems--buy a knockoff, lose your warranty AND your certification, critical if the filter system is for say a restaurant).