That is not true. Because the car has to function for the use the car is advertised for. If the car only can get 10 km on a charge, then it clearly does not function as a car anymore, and thus have to be fixed.Now and then, some journalist sum it up as "Tesla does not provide ANY capacity warranty, if a new car runs 10km on a charge, that's ok"
Also there is a difference between defective cells and degradation. A defective cell is a fault that should be fixed. But a degraded cell is normal wear (although this is not really a problem on Tesla).