Which actually seems reasonably fair; if someone takes a car and decides to tinker in the brake system and try to come up with their own antilock braking system they feel is better, that's fine. But if they then have an accident, they can't realistically hold the car manufacturer responsible for the ABS they modified.
Your analogy is flawed. It would make sense to say, you buy a car. Tinker with the brakes. After a while send it for "upgrades" ( say, they put in a fly-by-wire instead of the hydraulics ) and that "upgrade" bricks your car. You sue the manufacturer for the bricked car
A penny saved is a penny to squander. -- Ambrose Bierce