How is recalls per company a valid metric? Should it be at least normalised by number of models (e.g. if we assume design flaws)? By that metric Fords 58 are n

How is recalls per company a valid metric? Should it be at least normalised by number of models (e.g. if we assume design flaws)? By that metric Fords 58 are normalised by 40 odd models (only counting current) while Teslas 20 are normalised by 6 models (counting any car/truck build).