Site Admins should have access to all the content (read access as well as write access).
This rule is being broken in the case when a regular user restricts editing of a page only to him self (and optionally to other users).
In such a case the "edit" tab is not being rendered for site admins.
It seems that the problem is only in the code that renders the view, because the edit tab is accessible by manually creating the url i.e. http://mywiki.com/pages/editpage.action?pageId=23342
This should be easy to fix, so please fix it in the next release