They were teaching salon style, where the couple are closed at the man's right side & slightly open on the left side for walking, with a flexible embrace that opens a little more on the left side to allow for figures. The adornments that this head position allows for include, for example, allowing the woman to see & respond to the dibujos that the man may do with his left foot. Since these are adornments the woman's response is not lead.
I agree with earlier posters, and the bloggers who indicate that head position may vary according to the style of the embrace - salon or apilado. I also agree that in apilado there is no need for visual cues.