When does remove implies removal of parents and siblings?

I'm using the most recent stable Windows build:

C:\MyRepo\MyBranch>bzr --version
Bazaar (bzr) 2.5.1
  Python interpreter: C:\Program Files (x86)\Bazaar\python26.dll 2.6.6
  Python standard library: C:\Program Files (x86)\Bazaar\lib\library.zip
  Platform: Windows-7-6.1.7601-SP1
  bzrlib: C:\Program Files (x86)\Bazaar\lib\library.zip\bzrlib
  Bazaar configuration: C:/Users/dario/AppData/Roaming/bazaar/2.0
  Bazaar log file: C:\Users\dario\Documents\.bzr.log

Compare this interaction:

    C:\MyRepo\MyBranch>bzr stat
    unknown:
      File.txt
      Pippo.txt
      a/

    C:\MyRepo\MyBranch>bzr add a
    adding a
    adding a/Pluto.txt
    adding a/Topolino.txt

    C:\MyRepo\MyBranch>bzr remove a/Pluto.txt --keep
    removed a/Pluto.txt

Against this one:

    C:\MyRepo\MyBranch>bzr stat
    unknown:
      File.txt
      Pippo.txt
      a/

    C:\MyRepo\MyBranch>bzr add a
    adding a
    adding a/Pluto.txt
    adding a/Topolino.txt

    C:\MyRepo\MyBranch>bzr remove a/Pluto.txt --keep --new
    removed a/Topolino.txt
    removed a/Pluto.txt
    removed a

The only difference is the inclusion of option "--new" in the second one. The effect of "--new" is that also the siblings and parents of "Pluto.txt" are unversioned.

Consider also this example, in which also siblings of directory "a" are added:

    C:\MyRepo\MyBranch>bzr stat
    unknown:
      File.txt
      Pippo.txt
      a/

    C:\MyRepo\MyBranch>bzr add
    adding File.txt
    adding Pippo.txt
    adding a
    adding a/Pluto.txt
    adding a/Topolino.txt

    C:\MyRepo\MyBranch>bzr remove a/Pluto.txt --keep --new
    removed a/Topolino.txt
    removed a/Pluto.txt
    removed a

Again, "remove" with "--new" unversions the entire "a" directory, but not its siblings "File.txt" and "Pippo.txt" (showing that the "remove" command is still operating on "a" but it is unversioning too much).

Why Bazaar is behaving like this? Am I missing something?

*** EDIT May 11, 2014 ***

Also the following version is affected:

Bazaar (bzr) 2.6b1
  Python interpreter: C:\Program Files\Bazaar\python26.dll 2.6.6
  Python standard library: C:\Program Files\Bazaar\lib\library.zip
  Platform: Windows-7-6.1.7601-SP1
  bzrlib: C:\Program Files\Bazaar\lib\library.zip\bzrlib
  Bazaar configuration: C:/Users/Dario/AppData/Roaming/bazaar/2.0
  Bazaar log file: C:\Users\Dario\Documents\.bzr.log