I'm not sure were the author looked for information about architectural patterns but there is a separate section on it in the documentation: https://vuex.vuejs.org/guide/structure.html

This clearly outlines a suggested structure for non-trivial apps, where API requests are separated from the state management. It also references the Shopping cart example as a guide.

Due to this glaring oversight I can't see any criticism the author has as valid in the section about "Unclear architectural patterns".