and compared for the two gold standard methods LNO-CCSD(T) and fixed-node diffusion Monte Carlo (QMC) to produce a "platinum standard". Within our methodology, both approaches were employed with particular care to achieve convergence, see the "Methods" Section for more details. Their results were compared for 13 of the most challenging cases [biggest disagreements between the DFT results (PBE0+MBD) and LNO-CCSD(T), see Fig. ) of the SI] and found in agreement within their uncertainty estimates in 12 of the 13 cases (i.e. 92%) as seen in Fig. . The MAE between the two methods is 0.32 kcal/mol compared to 0.38 and 0.39 kcal/mol mean absolute value of the uncertainty estimate for QMC and LNO-CCSD(T), respectively.