A comparison is made between a typical intranuclear cascade (INC) model and the experimental inclusive slow (T0.4GeV) proton spectra in the p-C, C-C, and C-Ta in interactions at 3.3AGeV over a broad angular interval from 0° to 180°. It is found that the INC model reproduces rather well the inclusive slow and fast proton spectra, provided that the mean number of interacting protons (participants) in the corresponding angular interval does not exceed 2. The systematic discrepancies are identified and shown to correspond mainly to the noncovariant nature of the INC calculations.