I see. This news bit talks about receiving duplicate ballots. That is not an issue as the state is attempting to ensure that all voters receive their ballots. That doesn't make the state liable for voter fraud. As the LA County Registrar confirmed my assesment: "Making sure everyone gets the right to vote, err on the side of caution." They do check signatures for duplicate votes.
It is not illegal to receive duplicate votes. It is, however, illegal to send IN duplicate votes.