Are you guys kidding me. If all other inputs remain the same...

Are you guys kidding me. If all other inputs remain the same then extra CO2 will increase growth regardless. Not as much as if NPK and other inputs were perfect, but they are never perfect, ever. In fact we dont even know what perfect is for plants. Only a range of nutrient values that they do well in. And those values are different within that range for each type of plant.