Oddly enough, I can't think of a single book on dressage or any of the top dressage coaches that don't spend most of the time on the basic work that is being dismissed as "before" dressage even when working with horses at the highest levels. The heart of dressage training is the slow, progressive training of the lower levels and the development of correct gaits and balance.
Many many people in the western world see horses being thrown into very demanding work without any basic preparation of the back and suspensory systems. Class requirements are developed with a mature finished horse as the model, then young horses are expected to compete at the same level. Smart trainers discard any horse that might take time to prepare. Others try to force performance and ruin what could have been good horses. Some with good clients who will back them can wait and let a horse mature. Dressage testing is progressive testing at the lowest levels that allows the horse to be developed at the rate its bones, suspensory system and mind dictate and still compete. Having gaits and muscle development that are optimal for carrying a rider can't hurt. Thus Western Dressage as a competition.
As for collected work, I remember old film clips of horses in the Rose Bowl Parade and being shown in California in the 60s. I knew one of the women who rode. Those horse moved and carried themselves in collected gaits with suspension. Before someone tells me they were not working ranch horses, the woman I knew was the niece of Ed Connell, who trained ranch horses his entire life.