I saw a documentary where they stated that woman that look vulnerable are more likely to be assaulted.
So the confidence that woman show after such a course (although based on false skills) might indeed keep them safer from a possible assault.
That is not entirely accurate. What you are referring to has to do with self-protection skills, NOT self-defense skills. Few self-defense classes teach self-protection skills. My friend and I teach a self-protection course for women and our motto is "If you have to defend yourself, it is probably too late."
The attacker hunts for prey. They look for people who stand out from the environment, are typically unaware and preoccupied and visibly unprepared to respond to an attack. A confident look will not help a woman who is chatting obliviously on the cellphone or listening to the I-Pod, and has both hands filled carrying the day's purchases.