Why Imenu menus look differently depending on the underlying document types

[Denis Bitouzé]

Hi,

I wonder why the Imenu menus look differently depending on the
underlying document types: the table of contents tree is (for instance):

- fully expanded with (la)tex files, 
- expanded only at the first level with org-mode files (and sublists let
  us access to deeper levels).

Thanks in anticipation.
-- 
Denis