Training on tmQM showed that a subset of the data was consistently very poorly predicted, regardless of the hyperparameters or model used. For an illustration of this, see Figures and. These figures show parity plots, plotting predictions versus targets, for the training set. If the model were perfect, all predictions would exactly match the targets, and the points would lie on the y = x line. This behavior is somewhat expected since the predictions are in the training set, which the models were explicitly trained on. However, a subset of the data deviates substantially from the parity line, indicating that the models are not predicting those energies very well. This region is circled in red on Figures 2a, 2c trained models on the neutral subset of tmQM, and see that this region of underprediction persists even when charged structures are removed, which is shown in the SI (Under 'tmQM Test Parity Plots'). Additionally, we reconstructed several of the parity plots for models trained on tmQM, with the 155 structures that were removed in tmQM wB97MV excluded, both from the parity plot and from the summary statistics. We see that this exclusion has minimal effect on the summary statistics or the shape of the plot. This is shown in the SI (Under 'Effects of Removed Structures on tmQM Statistics'). We thus conclude that the region of underprediction is not due to the 155 removed structures nor charged species, and is a legitimate concern.