In this Letter, we show that optical smoothing of laser beams significantly broadens the CBET resonance compared to that predicted by conventional plane-wave models. In particular, temporal smoothing, as used in many high energy laser facilities, flow components normal to the CBET ion acoustic waves, and wavelength detuning significantly modify the power transfer between smoothed beams. We develop a model that quantitatively predicts the resonance broadening induced by these effects. We provide a simple criterion that identifies the laser and plasma parameters for which optical smoothing significantly impacts CBET. We apply these results to a TROLL radiation-hydrodynamics simulation of the NIF shot N210808, demonstrating significant modifications of the CBET coupling due to optical smoothing.