Now you are coming into the real world.
I'm firmly in it, I assure you, and teach couples of all shapes and sizes week in and week out.
You are missing a rather obvious point, that if the lady is not well matched to the man for height, the man places his RH where the lady's shoulder blade happens to be. It generally is to be found on her upper torso, well above the legs. I've yet to see a man trying to lift a lady off the floor for the sake of the ideal downward slope of his arm line. Perhaps in your "real world"?
As far as possible, the man's right arm will move, up or down (to find the shoulder blade), with an unbroken line from his shoulder to his wrist (ie the line is not broken by the elbow). The slope of the arm from shoulder to elbow of the left hand should match that of the right (ie the arms go up or down together), With the elbows at the same height, the LH to lady's RH handclasp will always work OK, whatever the height difference between the couple, and only if the difference is extreme, is any adjustment required.
There are all sorts of other issues regarding balance and poise and relative positioning, but the hold is usually quite simple to get right.