@hahaxd
You went from "it's simply not even possible to do" to "it's possible but it's bullshit", lol.
To add on the topic:
"Nanba-aruki" comes up regularly in martial arts, where it makes sense to have the hand in front be on the same side as the foot in front. Recently, a Koryū (traditional style) researcher named Yoshinori Kono has been talking about it. According to him, messengers from the ancient days would walk very long distances, sometimes several days in a row, using this walking form. The clothes in that era might have played a role too - women in kimono supposedly walked naturally like this.
Note that IIRC, he says that you're actually not supposed to swing your arms.
Personal experience: I got used to walking like this. It's weird at first, but nothing dramatic. I think if you really want to compare energy efficiency, you should experiment on someone being used to doing it, otherwise the comparison is flawed.