We report an inverse Raman-bleaching anomaly of oxygen-vacancy-activated phonons in underdoped YBa2Cu3O6.7 excited in resonance at 4.1eV. These modes are closely related to modes that photobleach under visible excitation. The resonance and selection rules match the prediction from the in-plane anisotropy of the dielectric function, as does their growth of intensity under illumination. These properties support the oxygen-vacancy-reordering model for photoinduced changes in underdoped YBa2Cu3O7−. We suggest that a similar coupling to anisotropic electronic resonances is responsible for the recently discovered anisotropies in the phonon dispersion.