Waves uses Harman target curve for tuning headphones. Also, they include generic EQ that is not a unit specific EQ. Best case tolerances are within +/-3dB, similar to other correction softwares. The USC is a calibration file made for your specific unit. It's super fine tuned to 1dB tolerance by playing pink noise through a live EQ until the frequency response on the IEC60318-4 ear simulator is matched to the target curve for your headphones model within +/-1dB 1/3oct RTA smoothing. In short, more than twice as accurate as generic correction solutions.