Ever notice that you can ask two different people directions to the same place, you often get two entirely different routes?
Are they both right?
As I've journeyed along my bellydance path, I often find that different teachers suggest similar techniques for some moves (a shoulder shimmy is pretty standard) but have variations as well. For that shoulder shimmy, do you just isolate the actual shoulder itself, or can you use the pectoral muscles to add sharpness?
Early on, one of my teachers (who I loved dearly!) taught a beginner's second level class. It was fun, but in all honesty, it felt like I was doing the same movement over and over without the next level growth I had been expecting. Move your shoulders back and forth only advanced to place your hands in a doorway to help isolate your shoulders.
This wasn't necessarily wrong, but I realized that I needed more. I learned differently, and processed things better when I had technical instructions.
Just using your "shoulders" to shimmy produced a soft, gentle shoulder shimmy. Adding in the pectoral muscles gave the movement power and allowed accents to bring it to another level.
Was either of these wrong? Nope. They were both right. They just produced different results and increased my dance "vocabulary."
Art is somewhat subjective, and having the basic tools mastered allows you to bring different levels to your creation. And learning from different teachers only expands your vocabulary.