I think there might be a bit of a misunderstanding.
What Westerman does is to compare legal scholarship with other scientific disciplines (similar to how we did it as well). She says that the common understanding of what scientists do is to understand phenomena that are external to them (e.g., like an astronomer who researches a certain planet movement that appears to deviate from what the standard laws of astronomy would predict. From this she infers that another, yet unidentified object may explain this movement). By contrast, legal scholars do not merely “observe” or “understand” the legal system, it’s not something external to them. Instead, she says, the main activity of standard legal scholarship is to put the millions of legal statements that exist (constitutional laws, regular laws, regulations, international and European law, court judgments, administrative acts) into relation with each other, attempting to put them into a coherent whole.
Obviously interpretation (which is just another word for understanding) forms part of this activity, but in a different way than e.g. in astronomy.