The conversion is set to MDV 0%, which uses the vertical FOV. And the vertical FOV doesn't change when you stretch 4:3 to 16:9, only the horizontal does, so the calculation results in the same number.
You hipfire conversion is set to MDH 0% here, which uses the horizontal FOV. And this FOV is different for the games you convert between, resulting in almost the same sensitivity when using m_yaw 0.0165 (since this value is most likely derived from stretching 4:3 to 16:9 which is (4/3)/(16/9)=0.75). When you do the same with the default m_yaw the sensitivity is different because it accounts for this difference.