Rydberg-atom microwave sensing based on electromagnetically induced transparency provides an optical approach to electric-field measurement, but its accuracy depends sensitively on the multilevel structure selected by the optical and microwave polarizations. Here we investigate the polarization-dependent microwave response of a cesium 34D5/2 Rydberg-EIT system coupled to the near-resonant 32F7/2 state and the nearby 32F5/2 manifold. In the parallel configuration, the spectrum is dominated by a nearly symmetric Autler-Townes (AT) doublet and is suitable for microwave-field extraction. In the perpendicular configuration, several magnetic-sublevel channels contribute simultaneously, and the off-resonant 32F5/2-connected branches produce asymmetric shoulders and branch-dependent peak weights. The main spectral features are reproduced by a multilevel model incorporating microwave dressing and optical Bloch dynamics. Treating the perpendicular spectrum as a simple two-level AT splitting is shown to produce a systematic field-inversion error. These results identify a polarization-induced limitation of nD-state Rydberg antennas and provide guidance for quantitative microwave electrometry.