No dependence of electroreflectance line shapes upon polarization direction or crystal orientation is found for any core-level electroreflectance structure from the Ga 3 dv core levels to the conduction bands in GaP. Matrix-element effects that are responsible for anisotropy in sp3 valence-conduction-band electroreflectance spectra appear to be too weak to be detected in core-level spectra. The result may be general. The field-induced modulation line shape, Δɛ1, for the Ga 3dv32,52-Xc6 critical points is obtained from the dependence of the spectra and the generalized Seraphin coefficients upon angle of incidence. The line shape is further analyzed to obtain the Δɛ1 spectrum for Ga 3dv52-Xc6 alone. This procedure yields a spin-orbit splitting Δ3d=0.43+/-0.02 eV. A weighting of 0.65 +/- 0.05 is also obtained for the j=32 band relative to the j=52 band. This is in good agreement with the 4:6 ratio expected on d-band occupancy, showing that the matrix elements are also independent of j. The line shape of Δɛ1 is in good agreement with that predicted by the lifetime-broadened, Coulomb-enhanced Franz-Keldysh theory given by Blossey. The line shape shows a broadening of 160 meV for this transition, and a momentum matrix element about 1/3 as large as that characteristic of sp3 valence-conduction-band transitions.