An example such as this Trailhead one:
has distinct role names everywhere and so it is easy to understand the statement:
Users at any given role level can view, edit, and report on all data owned by or shared with users below them in the role hierarchy
But what happens if the role names repeat e.g. there are 4 "VP Development" people with the 4 teams below them in the tree using the same roles names? Given that there is e.g. nothing that identifies which "Director Product Management" reports to which "VP Development", each "VP Development" can see all the records of all the teams?
So presumably all the the role names need to to be unique to each team to keep the records private?