You've seen these rules before, with a slightly different page format and less wording. But I'm re-working the "Basic Concepts" chapter, and so as part of that effort it's been broken off into its own sub-section.
The reason I'm working on that chapter, and not the combined "Combat Phase" is because with our system more or less settled, I can go through this chapter first, and pull as many of the existing Moving, Shooting, and Melee phase rules into it as I can. Because I don't want the combined Combat Phase to be some monolithic 20-page monster.
Along the way, I'm also working in some rules that I hadn't thought of, or fully worked out before, such as basing standards and unit movement types.