The non-proximity of W3W locations with similar identifiers is intentional; it's meant as an easy way to perform error checking. The concept is that you state your location, and if you state it wrong, or the other person gets it wrong, the mistake will be obvious because the small change to the identifier results in a location extremely distant from you.
The system pretty explicitly considers all squares equal, without a hierarchy such as you envision. There are no identifiers for larger agglomerations of individual squares.
(And more specifically, where identifiers are hierarchical, you generally have the larger scope first, not last. URLs are a bizarre exception.)
