I never understood the liability aspect of vehicle repair from a manufacturer's standpoint. The common refrain seems to be that these new vehicles are not serviceable without the dealership/manufacturer. It seems to be a narrative to drive out the owner from repairing vehicle or independent repair facilities.

The liability seems to be the same as historic vehicles, for... vehicle repair. So why is this any different?

The burden of proof is on the manufacturer to prove that a modification caused damage to the vehicle.