Comparison of molecular gas masses inferred from different sets of observations for our three QSO hosts (top three) and the literature sample of z ≳ 6 QSO hosts (bottom nine). For the CO-based values, we have assumed a ULIRG CO-to-H₂ conversion factor of α_CO = 0.8 M_⊙ (K km s⁻¹ pc²)⁻¹. We show two masses for CO(2–1), one derived without any CMB correction being applied (filled blue circles) and one derived by applying a correction assuming the high-density (n_H2 = 10^4.2 cm⁻³) and high-temperature (T_kin = 40 K), non-LTE scenario presented in da Cunha et al. (2013a; blue outlined circles). We also show molecular gas masses derived from [C I] (2–1) emission (green squares) assuming the [C I] is optically thin, in LTE and has the same abundance as the sample of lensed starbursts studied in Harrington et al. (2021), namely [C I]/H₂ = (6.82 ± 3.04)×10⁻⁵. We also compare to molecular gas masses derived from the dust masses fit here, assuming the local gas-to-dust ratio of 100 (red triangles), as well as molecular gas masses derived from the [C II] 158 μm line luminosities, assuming the mean [C II]-to-H₂ conversion factor (α_[CII] = 31 M_⊙/L_⊙) derived by Zanella et al. (2018).