I think those technologies are mentioned throughout the book - just at a much larger scale in the second part.

Bolos are used for spin gravity in the first part, but that's very different from the rotovators used in the second part. Both in concept and design. The key point with the rotovator is that the tip is moving at ~0m/s relative to the body it's orbiting when it's at its nadir, allowing you to just hop/grab on.