I think you are comparing apples to oranges. I do not believe that knowing how to dance one dance helps the other all that much. Ballroom is done with a partner in close hold. How you dance depends a great deal on your partner, whether leader or follower. I have found that people who have danced other styles often presume they will have an easier time of it. They don't. We had a professional contemporary dancer in out studio struggle with triple swing. Body position and frame is everything in ballroom. Just keeping your arms up is a chore. If you watch the dance shows on TV, you will see that the hip hop dancers struggle with ballroom. If you have danced other styles, you will have an easier time with music and finding the beat but that's about it. Others may disagree, but this is what I have seen after working in a ballroom dance studio for 10 years.