In MSBooster ion mobility features are not included in the default set of features, as they only marginally improved identifications. The limited benefit of ML-based ion mobility features may be explained by the high dependence of the CCS on the precursor mass and charge. Because decoy PSMs have the same charge and a similar mass as the unknown true target peptide, their CCS predictions are highly correlated with the experimental values. Potentially more relevant features are simply the peptide mass, length, charge state, and experimental ion mobility value.