[en] Highlights: • Optical and EPR spectra for CaSGG:Yb"3"+ and LuGG:Yb"3"+ garnets were explained. • The reliability and standardization of fitted CFPs were performed and discussed. • The unavailability of SPM for LuGG:Yb"3"+ garnet was found and analyzed briefly. - Abstract: The crystal-field modeling based on superposition model (SPM) for the orthorhombic Yb"3"+ centers in Ca_3Sc_2Ge_3O_1_2 (CaSGG) and Lu_3Ga_5O_1_2 (LuGG) garnets has been employed to explain their recent experimental optical spectroscopy. Furthermore, the electron paramagnetic resonance (EPR) principal g values for orthorhombic Yb"3"+ centers in LuGG garnet have been interpreted and the predicted g factors for CaSGG:Yb"3"+ garnet are also given. Both calculated optical spectra and EPR g factors for the two Yb"3"+-doped garnets could be regarded as in reasonable agreement with the experimental ones. Two important facts about reliability and standardization of the fitted phenomenological crystal-field parameters (CFPs) have been discussed and the unexpected unavailability of direct parametric modeling by SPM for LuGG:Yb"3"+ garnet is also found and analyzed briefly