Prior to training the ML models, we evaluated how closely the SQM approximated the DFT calculations. This gave us a rational, dataset specific context to consider alongside the widely accepted 1 kcal mol -1 threshold typically used in evaluating reaction barrier/energy predictions. For ds1, 8 ds2, and ds3, their pre-ML SQM-DFT metrics are reported in the literature, Table , and in the ESI, section 4.3. For ds4, the pre-ML AM1-DFT MAE for reaction barrier prediction is 10.46 kcal mol -1 . The spread of distortion and interaction energies are shown in Fig. . Fig ) and e) highlight that AM1 significantly overestimates the dimethyl malonate distortion and interaction (pre-ML MAEs of 3.70 and 10.83 kcal mol -1 respectively) energies. The interaction energy is calculated from the reaction barrier and distortion energies thus, its pre-ML AM1-DFT MAE could be impacted by the compounding of errors from the lower level of theory across multiple calculations. It could also be rationalised in part by the inability of the parent method (Hartree Fock) to account for electron correlation sufficiently and thus important interactions are not well captured. The interaction energies are also overestimated by AM1 across the other datasets. For full information on pre-ML metrics see ESI, section 4.3.