About Alexander: some of his ideas were shown to be scientifcally viable, and some obviously not. The same is true of any charismatic person who finds solution to everyday problems. Typically in things like this, they are ideal for people of normal body-types who don't suffer abnormal problems such as scoliosis, or some extreme debilitation. Similarly, the founder of the Gestalt method of therapy, Frederick Perls, had a lot of scientific backing on his way with more or less normal people, but even he confessed his method was useless when it came to psychotics.
I love the idea in Alexander technique about debauched kinaesthesia, and it is an idea that has influenced my thinking alot. It is one of the main reasons why I oppose almost all teaching from a physical point of view - if you direct a person to do something specific with their hands, elbows or arms, more often than not you create great confusion, and have the person doing something totally unrelated to what you asked. Not only that, but the movements you are desvribing are most likely false.
Bernhard touched on this when he said you should watch what great pianists, teaching, do, not what they say, and even provided a memorable example of Liszt's teaching, where what he said about octaves (how to play them physically), was not at all what he was doing. There we have a perfect example of debauched kinaesthesia (I also love the Victorian language.)
In short, students should know how the various parts work and work together, but they should rarely if ever be told what to do with those parts specifically.
Walter Ramsey