Usually when people do make studies and take a hard look at people a common attribute comes out: both men and women are human. The idea that female-in-power is less likely to abuse assumes that there is some form of biological sex or gender role difference that is so dominant that human behavior diverge. The Amygdala is not bigger or smaller depending on sex, which mostly leaves culture and gender roles to explain why we don't often hear about abuse in female-in-power relationships.