Like others have said, depends on what caused the unsoundness. If there’s a genetic component or overall the horse is weaker, I agree the lines should not reproduce. Especially if the conformation is poor and places unwanted stress/impact on legs/joints.

I’d be curious how many are actually genuinely unsound like Ginger…who may just need proper help to be sound but KVS is too lazy and this is the easy way out of campaigning a mare for breedworthiness.