We have shown throughout our analysis here that the problem of compositional disorder is not well addressed by the methods used in the A-lab paper, with many predicted ordered compounds likely to be known, disordered analogues. It should be considered how fundamental this problem is to the materials prediction field. As discussed earlier, compositional disorder is well accommodated by the equations of crystallography: fractional occupancies can be entered in the structure factor equation. However, fractional occupancy presents difficulties for many computational methods. This issue has long been recognised. An early approach to model disordered materials is the virtual crystal approximation, (VCA),