Can't even define it right: "For example, a person labeled “female” at birth who comes to identify as a girl, then a woman, and behaves in ways expected for girls and women, can be considered cisgender. This, in contrast to the term “transgender,” which describes those whose gender identity and presentation differ from that expected for the sex they were labeled at birth."

Cis is labeled as behavior, which would imply a tomboy is acting trans. Then he switches to presentation to describe trans. Seems as if he doesn't want to deal with cis people who are gender non conforming, because that ruins the narrative.