If a hierarchy filter is "ragged" then it can look quite confusing to users to see levels such as (empty), (empty), (empty). Especially when using the filter to represent things like folder type structures.
It would be great if the hierarchy filter had an option to "trim" the hierarchy with respect to how it is rendered when it reaches an (empty) level which has nothing but (empty) values lower down in the hierarchy. i.e. the hierarchy has ended down that particular branch/