Maybe not. The cooking in the northern (Mexican) state of Chihuahua is quite different from that in the Mexico City region. Could she have been referring to that?
It is possible. She was saying that in order to prepare a roast in northern states it was not necessary to wash the meat due to the stricter processing regulations. While in the southern states it was recommended that that the meat be washed before beginning the preparation due to the less strict regulations.
I thought she was referring to different countries.