that is what we try to study in this course — “methodology” is the knowledge about methods. Legal writing mixes up tons of different things — describing the law+legal interpretation (“legal method”), critical analysis of the arguments used by a judge (“discourse analysis”), prognosis of future outcomes (this could be done with quantitative methods, but often legal writers just make personal guesses), policy recommendations, etc. But you are right that legal scholars never clearly distinguish between those — and neither do you have to when you are writing. However, it is important to be able to understand what others do, in order for you to not be tricked by what others say.