The book does not tell you what to do, instead it tells you the positions you will find yourself in during the course of doing the right thing. It is not literally instruction, but instead a checklist.
Of course you can take the checklist of positions, think about them, and figure out the path of movement that would join them together. The figures that we think of as having swing are those figues whose waypoints describe a path of motion linked by the kind of multiple-step three-dimensional trend that we have come to call swing. It's there in the rise and fall, the sway, the footwork, etc. You won't be able to create all of those elements in a consistent way without swing - so swing is implied, but not stated.
Another thing to keep in mind is that swing in the era when those books were written was far more subtle than it is today, and so may not have been a major topic in lessons. Movement then was rather small, stiff, and stilted to the modern eye. Which makes it so impressive that authors who danced in such a (to today's eye) "muted" fashion did understand the role of swing and how it would evolve the body position, in a way that has held true even as successive generations have turned up the volume of swing to the point where flaws in the reasoning would become obvious to all.