May 2020 Prescribed Title #5 is focused on whether a particular situation can be understood with one theory or if multiple theories are required since every single theory has limitations.
A constitution is a legal document and in theory it can be completely understood from a legal perspective (i.e. a particular legal theory).
A constitution, however, is more than a simple set of laws. There is a tremendous amount of context and this could mean that more than a single legal theory is needed to understand a constitution.
In the case of the Japanese constitution, it was written under the supervision of the occupying U.S. military after WWII. Much of the Japanese constitution was not written by Japanese authors, but American ones. There have been changes in the way the constitution has been interpreted (e.g. Article 9) and understanding these in depth means looking at the constitution in a number of different ways.