want commits to bound branch to update master branch's tree

I have a shared Repository, accessible by the file protocol (actually a Windows "file server"), created with the option --trees. We use the "Centralized" workflow ("lockstep"), all users use check-out/update/commit from/to centrally store all version (in one branch).
This works ...

However, I used the "--trees option, when creating the central repro and *assumed* this means any commit will automatically update that central directory. Such, no-bazaar-users can read/browse the "latest" version of each file.
This however does not work!

Manually doing "cd <central/repro/branch> ; bzr update" does work. Then the result is as I expected.

When not using checkouk/commit, but using an (*assumed* almost the same) local branch, with a 'bzr push' them to the central repo, the tree there is updated!

Using latest stable windows version of bzr
>bzr version
  Bazaar (bzr) 1.11rc1
  Python interpreter: C:\Python25\python.exe 2.5.2
  Python standard library: C:\Python25\lib
  bzrlib: c:\python25\lib\site-packages\bzrlib
  Bazaar configuration: C:\Documents and Settings\XXX\Application Data\bazaar\2.0

Central:
       mkdir f:/Repositories/Bazaars/Proj
       cd f:/Repositories/Bazaars/Proj
       bzr init-repo --trees . # note the DOT
       bzr init sprint

Dev:
     cd ~/work
     mkdir Proj;
     cd Proj
     bzr checkout f:/Repositories/Bazaars/Proj/sprint
     cd sprint
     touch aNewFile
     bzr add aNewFile
     bzr commit -m "the file is stored in the repro, but does NOT appear at f:/Repositories/Bazaars/Proj/sprint/aNewFile 'automatically'"