You know, I’m not sure how accurate this is. To give you an example - I would normally hold hands with very little contrast or strength, but yet I’m not a passive person. The way I hold hands does show something about me, but the interpretation is not necessarily so straight forward in all cases.
Would be great if you can tell more about what you learned (the meaning of certain styles/ movements), or give an example.
As far as feeling how passive or assertive your dance partner is, I was looking at this primarily though the eyes of a follow. When I’m dancing, I’m waiting for the lead to initiate the movement. Each lead will do this with a different amount of speed, pressure, motion etc. In my own dancing I have run across some leads who are tentative, and just don’t seem to have the confidence to direct me (luckily most of them improve quickly or stop dancing). On the other end of the spectrum there are leads who are extremely direct, for them every beat of the dance is controlled. Most leads fall somewhere in-between. By feeling a man’s lead I can get an idea of how assertive he is. Of course it is important to take in to account his personal style and dancing experience.
I think you are right when it come to the follow. It is her responsibility to wait for direction from the lead so there is little opportunity for her to be assertive during the dance, but I think she still has ample opportunity to display confidence. For example when the lead releases her temporarily for a free spin or other individual movement some follows will rush back to the lead in a panic to have guidance again. On the other hand a confident follow will continue the move with the same speed and direction she received form the lead and will only stop when the lead comes back to her. As the level of dancing progresses the individual moves can become quite elaborate. It seems to me that the more confident follows take more advantage of these unexpected breaks in connection. They are not thrown off because they have the guts to handle being left alone without much warning.