Once the leader's hand is on the follower's back, the follower (with hips parallel to leader's hips) twists torso right to settle into the leader's hand.
The twist comes from lat muscles.
This twist is what allows the follower to connect to leader's RH, as leader's right arm cannot be parallel to their body (hand is slightly further away from leader than elbow).
The twist is very visible in tango and waltz, it still exists in foxtrot but is not exaggerated there.
In closed position, partners' hips are parallel but follower's upper body is turned away from the leader slightly.
When in promenade position, the upper body retains the same position that it had in the closed position and hips unwist relative to it. For the follower, when transitioning between closed position and promenade position there is no movement in upper body as upper body is essentially already in promenade position.
In closed position, partners are offset so that each person's head is aligned with the other person's right shoulder.
When in promenade, the follower then is slightly behind the leader.
Promenade Head Styling
In closed position, follower's head is pointed over leader's shoulder. When going into promenade, say in waltz, on 2-3 counts as the hips untwist (see follower's connection above) the head turns from looking at leader's right shoulder to looking toward follower's right. When going from promenade to closed, on the same 2-3 counts the head turns from follower's right to over leader's right shoulder.