"For me twisting of the spine is. With feet parallel turn your shoulders to the right and your hips to the left. A very uncomfortable position to be in."
Sure, if you do it to that extreme. But this is indeed what happens TO A MUCH SMALLER DEGREE in fully skilled ballroom dancing.
"Another page under CBM. Care must be taken not to turn the shoulders independently or an ugly dipping motion will result."
Yes, but this is still not a blanket prohibition against body twist, instead it is a warning about using a counterproductive twist in a situation where something very different is called for.
I find the most notable examples of body twist occur in situations where you turn your hips before your upper body - which is basically the opposite of what your citation warns against.
"Back to the twisting of the spine. There is nowhere that I can see where it tells a student to twist the spine."
Nor is there any blanket prohibition against it. Nor, quite obviously, is the book description anywhere close to completely capturing what advanced dancers actually do.
With the noted exception of the body twist necessary to achieve a clean promenade position, twist in the body is a fairly advanced topic which shouldn't really be raised with beginners - because as the book points out, other things are far more important.
"If I were to twist my body. Ask your partner does she feel she is being asked to go to two different directions at the same time. I think she will say yes."
If I do it right, she will match me by moving different parts of her body in different BUT COMPATIBLE ways, as necessary to achieve the desired result. But if you do it wrong, you will be asking her to do two CONFLICTING things with her body.
However this is an advanced concept that's not going to come up in most lessons and especially not most written descriptions. It's a lot easier to get it wrong than to get it right, so most teacher comments on the subject of twist are going to come down to "don't do it" - the actual encouragement to do the proper kind of twist will come later, and is as likely to be communicated by feel or by allusion as to be stated literally "twist your body this way".