Emulator performance on mocks with different phase. In the upper panel the 25 realisations of Planck 2018 cosmology using the median HOD are shown in grey. The average is shown in red dotted line. The 25 residuals for both IGP (green) and MGP (blue) predictions are shown in the bottom panel. L⁻¹ is the Cholesky decomposition of the inverse of C_tot. The grey shaded areas correspond to 1σ and 2σ deviations.