I don't think it explains those Guangzhou southern styles that got exported to the west; Hung Gar, Choy Lee Fut, Lama Pai, Hop Gar. These southern styles, don't have the three step formula, have both battlefield and farmer weapons, do generate power through the legs.
Agreed. Hung gar has maybe the clearest power generation by transition from one stance to another. Mok gar and Choy Li Fut has similar ways using footwork and transitions to generate power.
What is more interesting than footwork, IMHO, is to compare breathing techniques and methods. Here you can see very clear differences between northern styles and Hakka arts for instance. The breathing methods are also something that affects the use of legs and stances and practice of postures. So if you go from this direction and first understand the differences in breathing and internal aspects, then it’s also more easy to understand the differences of the legs and footwork. Again, IMHO.