IME, the suggestive influence works largely, as you said, unconsciously, and automatically. In duality, it is not purposeful manipulation, but a coming together of two people influencing each other back and forth, agreeing on goals and methods on a psychological level. It is meeting the other person with input that serves the other person best. Whereas in other relationships people try to manipulate another into goals and methods that to some extent is not what the other agrees with or feels natural at.
I work as a chef for a temp agency. Sometimes I work with SLI chefs, and these moments are bliss. Everything runs smooth and tasks are easily distributed without a lot of discussion, often even without discussion at all. Not only during work, but also when taking breaks. thus the more private moments. If I were to summarize the nature of dual relationships, it would be that they are "let it be" relationships.