This is the actual definition of "cargo cult" behavior.
It's getting cause and effect backwards because you don't understand their relationship, and trying to imitate the effect in the futile hope that it will cause the cause.
People who sit all relaxed like that do so because they have power. They don't have power because they sit like that, and sitting like that will not magically confer power to you.
I took burlesque dance classes for a while. One of the things taught in this class was how to look confident, because projecting confidence is also pretty damn sexy.
Curiously enough, as I started learning these postures and using them, I found myself becoming a lot more confident. This was not something anyone told me to expect; it just sort of happened. It's spread out over a lot of how I move and behave, even when I'm not explicitly turning it on.
You are not a mind riding on top of a body. You are your body. And your body has a lot of weird feedback mechanisms that can be exploited.
If you read the article, they actually do an experiment and show via random assignment that assigning the posture actually causes the outcome (in this case, job interview success).
They didn't show the mechanism, but they did in fact show the direction of causality.
It's getting cause and effect backwards because you don't understand their relationship, and trying to imitate the effect in the futile hope that it will cause the cause.
People who sit all relaxed like that do so because they have power. They don't have power because they sit like that, and sitting like that will not magically confer power to you.