hierarchical taxonomy term uniqueness

during developing a module which programmatically creates hierarchical taxonomy terms like this (with number of nodes corresponding to term in parentheses) ...

* bar
- foo (1)
* baz
- foo (1)

... i came across a weird observation:

for faceted_search to properly work on the automatically created terms i had to click on admin/content/taxonomy/[vid] (save) which i think calls http://api.drupal.org/api/function/taxonomy_overview_terms_submit/6 -- if i remember correctly after that, or somehow along the way my "baz > foo" - nodes were attached to "bar>foo" instead:

* bar
- foo (2)
* baz
- foo (0)

so currently i ended up to create

* bar
- bar.foo (1)
* baz
- baz.foo (1)