In the past, it was taught that the man's right hand should sit snugly under the lady's shoulder blade. This was at a time when the lady's stance was more squarely in front of the man.
In recent times, the man is more to his left (relative to the lady) and the more modern positioning of the right wrist and hand follows from this. Nowadays, the teaching is all about contact with the right wrist, and the right hand just nestles wherever it finds itself as a result. Things do change. That's progress.