Shashin, can you elaborate on this and how not having tilt\swing on both standards would apply toward macro product photography?
Front standard controls the position of the plane of focus. The rear standard controls the plane of focus and linear perspective.
I can use the front standard for making the plane of focus intersect the object at an angle--imagine shooting a watch face at an angle, I can have the plane of focus follow the watch face by just using the front standard.
Now I have a cylinder shaped object and I want to shoot it an angle. However, I want to keep the sides of the cylinder parallel, I could then use the rear standard parallel to the length of the cylinder to keep the lines from converging. (I can also swing the back away to give greater linear perspective by making the lines recede faster.)
So there are two basic conditions for focus:
1. When the object plane, lens plane, and sensor plane are parallel--shooting the brick wall type of setup.
2. When the object plane, lens plane, and sensor plane intersect. By using the front standard, perspective does not change from the POV. By using the rear, you influence the perspective. And you can use both for greater control over perspective.
The art of controlling perspective with the rear standard seems to be less used today. Most examples I see on the web only show examples with fixed backs.