"Hey you guy who are into physics."
Twisting the spine / around the spine should not be done not done to create torque!
It is done to keep the body shaped to the partner while moving both bodies in a direction which doesn't happen to match the seperation between the partner's centers.
"If I twist my spine on a dance step am I trying to go in two different directions at the same time."
No, but you are trying to shape in one direction (towards your partner) while moving both of you in another direction.
"Am I signaling one thing to my partner plus another at the same time."
Yes, but they don't overlap. You signal connection and you signal movement. The directions don't have to match - in most dance figures they can't.
Confusing your partner is not good of course. But twisting around your spine does not necessarily mean confusing your partner if you do the proper way. Indeed, it is a basic element that makes many of the linear movements in ballroom possible. Without it (watch the couples who refuse to ulitize it) you end up having to curve many things around each other, instead of simply moving together in the intended direction. Some finds those curves aestheticaly pleasing. Others have a use for curve now and then, but like to be able to dance the numerous straight line figures along the straight lines of progression as they have been written.