No, this is a distinct argument. It's that this system was designed to function best when everyone does their jobs. Attorneys in the US are supposed to be zealous advocates. The judge and jury don't know going in whether the person did it or not, but the hope is that if the prosecutor fights their hardest (even if the accused is innocent) and the defense attorney fights their hardest (even if their client is guilty) that hopefully ultimately the one that comes out ahead will be the one that's right. It's not a perfect system, but this is how it's meant to work.