You're referring to #4422 I believe.
The difference here is that the logout link is in the general Trac navigation (metanav in this case), so we can't assume that the Wiki component will always be available. We therefore can't redirect to "LogOut" or something. But it should be possible to do this with a simple configuration setting, if wanted.
The idea of being able to configure the default location of the navigation entries is a follow-up of the "Discussing two changesets" trac-dev thread. So I'd like to come up with a consistent solution, and I even found a pre-existing ticket for that, see #2060.
