Warren,
My comment was with regard to the specific outlined example: leading the lady to step forward exiting the 123 of a reverse turn in, yes, Standard, foxtrot.
As I said in the previous comment: I don't dance standard.
Having said that, as far as I've seen in any dance, if something provides enough pressure or tension to create any tension or pressure, the tension or pressure pattern will vary at least somewhat. Maybe there is some exception in standard, but I find it difficult to believe based, partly, on physics.
There are times when the lady might feel pressure from that hand, such as centripetal force maintaining her rotation in a standing spin - but in that case, the pressure would actually provide support, and not just a lead.
In some moves I do feel the force required to provide centripetal acceleration. Of course this provides "support" -- anyone moving in a circle needs the inward pull. But at initiation and ending this force also changes largely because we are changing speed. But the continuous nature of lead follow will also generally mean the lead will generally have some aspect of the connection changing especially near the end when he wants to initiate something new. At that point, I will feel pressure in a different place, or directed slightly differently. It's not just a dimminishing of the centripetal force that results from moving at a lower speed.
Smooth doesn't have this exact movement, and the traveling movements are more likely to be at an angle such as outside partner; I think in those cases I might be providing an indication at the wrist, though still not through pressure in the palm of the hand.
Depending, in traveling moves I'd generally have arm/body/hand has contact in varying degrees. Other than some turns, I rarely get the sensation of having contact with a wrist on my back. But who knows? If it's out of my line of sight, I only know that I feel some amount of pressure in some spots. In shadow position, I often feel contact by a palm on either the rib cage or hippular area. (I need to assist that contact.) I also might feel a whole arm. In some turns, I do briefly feel hand on back, with some accompanying arm motions.
The common "lie to children" here is that the leader should always maintain a constant, and even rigid, frame. The "hands belong to the lady" concept is a step toward more sophisticated use of the "frame" by allowing it to "breathe" - but within limits, without returning to wholesale pushing or pulling with arms and hands.
Honestly, taken literally, I don't know what the phrase "hands belong to the lady" actually says. Obviously, the lady doesn't actually take over your hands and move them arbitrarily wherever she wishes. So there must be quite a bit of context or an additional paragraph elaborating that to leads.
The only thing I can respond to is this
"I was taught that my hands belong to the lady and should stay with her, so ideally you won't feel any difference in pressure on your back -"
I
do feel differences in pressure on my back in any dance and any move
where there is enough pressure to create a connection. Maybe standard is different from all other dances, but I dont' dance standard.
The only time I
can't feel variations in pressure in my back is when I
feel no pressure at all! So either there is no connection in the pattern (there isn't in some), or the lead doesn't provide connection or I screw up and don't settle into the connection.
Anywhere there is connection, I can sense changes in pressure tension, distribution and so on. I may not respond. I may be confused. I may get mixed signals. But I don't think there is ever a connection that has an absolutely constant pressure.
The thing is: there is a lot of information communicated by the leads state of motion and connection. It might not all be information he thinks is "the lead", but it does tell the follow something. (Some of the information can be misinformation, especially with an inexperiencee lead.)