Theoretical angular power spectrum for our three redshift bins. The Limber approximation is represented with a dotted line, while the exact computation is presented in Eqs. (31) and (32) with a dashed line. The convolution with the mixing matrix is shown, respectively, with a solid line (Limber approximation, i.e. the model used in our analysis), and with a dot-dashed line (exact computation). After the mode-mode coupling, the Limber approximation deviates only for ℓ ≲ 10, i.e. for the angular range already excluded from our analysis (gray shaded region).