Comment 6 for bug 633695

Yes, --freshen will skip uninstalled, while --replacepkgs will re-install already installed,
leaving the corner case of what to do with --freshen if "same" package is claimed to
be already installed.

The reason for the corner case is that already installed packages might be
modified and its not clear whether "skipping" or "re-installing" is the desired intent.

FWIW, I suspect (unchecked, just I know the code) that "--freshen --replacepkgs"
works just like "--update --replacepkgs" but will also skip uninstalled packages.