This picture shows the common mode gain of the input stage. Since the differential gain is unity, the common mode rejection ratio (CMRR) is the inverse of the common mode gain.
>100dB suppression in the 50Hz...100Hz region is a pretty darn good value for an OPamp based solution. So the resistor matching work has paid off. With an audio transformer you could reach up to around 120dB CMRR in that frequency range.
But also the close to 80dB @ 20KHz are outstanding and such a high value is typically not even reached by transformers (but please take note that this measurement has been performed under lab conditions with no source imbalance).