Non-hierarchical, non-directional linking between notes provides better information over time than hierarchical categorisation. Categories must by their nature focus on one phenomenon of a thing and therefore are restrictive compared to rich linking in multiple directions.
Backlinks “may” be used to infer hierarchy, but it cannot be guaranteed that is the case. They are more likely to reflect the order notes were created.
This does not preclude a Structure note from creating a hierarchy where it is beneficial to understanding relationships between notes.