Possible bug: hooks/post-update does not trigger

Sort of a problem is that hooks/post-update script is never triggered.
I have the following setup:

I work on a local repository and publish my changes by pushing them into
a bare repository which lies on the same filesystem. The actual
publishing will then require "git update-server-info" and rsync'ing the
bare repository to another host which in turn serves the repo via http.
(No git installed on the remote side and probably never will.)

I want to make this process automatical and I have actually done it
already with hooks/post-receive. It works fine. I'm just wondering why
hooks/post-update doesn't work.

The default hooks/post-update contains the line

  exec git-update-server-info

So the file is sort of advertised being the "official" way of running
git-update-server-info. The problem is that on my bare repository side
that file never gets executed (yes, execute bits are on). I tried to put
"echo" and "touch stampfile" type commands there but nothing happens.

Well, my problem was solved simply by using hooks/post-receive instead.
I put the following lines there and it works great:

  git update-server-info
  rsync --recursive --delete . remotehost:public_html/repo.git

Still I'd like to know if there is a bug in hooks/post-update triggering
mechanism or did I do something wrong?