Hmm, maybe it is because I use Shortcutd.

So, I have now uninstalled cl-launcher and shortcutd to check default behaviour without them installed and the original camera app doesn't start on a half press with the lens cover closed, but does when the lens cover is open, your version starts on a half-press even with the lens cover closed. If necessary I can do a clean flash of my spare N900 to check behaviour on that, but I don't remember it ever starting on a half-press before I installed shortcutd, but my memory could be at fault here.