I agree 100% with Roshanna when she says,
The problem with 'watch and follow' for beginners in bellydance is that so many of our new dancers are not only adults, but do not have any previous relevant movement background, and so have not developed the motor skills to learn in this way.
Actually I think even some experienced dancers may not be able to "see" the muscles moving. I came to belly dance in my fifties with a background in ballet, jazz and flamenco and I had my own instinctive way of approaching the movements, but I wasn't consciously "seeing" the muscles the teacher was using. I do know I was able to mimic the movements far more accurately than my classmates though, because I had a much better spatial awareness (i.e. I knew exactly where my arm or leg was in space - something that people with no dance experience often don't know!).