I feel like like the term "theory" is somewhat subjective with regards to how it is being used for music. In science a theory is "a well-substantiated explanation of an aspect of the natural world that can incorporate laws, hypotheses and facts". From the discussion I would interpret theory as a set of rules used to achieve some musical effect. It is much squishier because there is likely a large set of music rules that can achieve similar results. In science that is also true but usually the simplest set of rules are chosen that satisfy the conditions. Seems like the scientific approach would be rather limiting for music - making it rather tedious and boring instead of inventive and interesting.