Moreover, bond-additivity corrections consistently provide substantial improvements over relying solely on atom-energy corrections. Across all test scenarios, ∆H • f values computed using only AECs exhibit relatively large errors, whereas applying BACs substantially lowers these errors. This improvement is particularly evident for neutral singlet species, which are well-represented in the training set. For more exotic triplet and zwitterionic species, BACs still enhance accuracy, although to a lesser degree than in neutral singlets. The presence of significant outliers in the challenging test set when using AEC-only corrections suggests that the performance gap may arise not only from insufficient fitting of bond types but also from the inadequate treatment of unusual electronic states associated with these underrepresented species. These findings highlight the need for developing more specialized AECs and BACs tailored specifically to less common species such as triplets and zwitterions. Furthermore, expanding the reference database to include high-accuracy thermochemical data for these species is crucial for improving the robustness and transferability of ∆H • f correction schemes.