Wow, I guess some people really have to reach deep to achieve some sort of victimhood status.
Based on the other Shep animations (walking through the Citadel for example), I'm guessing there were separate male and female motion capture actors, at least for Shep.
That being said, the way they react comes down to basic physiology:
Men accumulate fat in their belly and waist region, (ie beer bellies), so male Shep would run his hand across his six pack to make sure it's still there.
Females accumulate fat in their hips and buttocks. Thus femshep uses both hands on the sides of her body to make sure she still has the ideal waist-to-hip ratio of .7.
This differentiation was either achieved instinctively by the mocaps of each sex, or was added in because Bioware understands basic biology. To call it "sexist" is ridiculous.