Last modified: 2008-04-17 19:16:11 UTC
At the moment the page editing routine is specific for wikiUI-editing, and thus prohibits other types of interfaces to easily edit pages (for example the API).
This is happening right now with Article.php, EditPage.php will follow. For progress see the apiedit branch at http://svn.wikimedia.org/viewvc/mediawiki/branches/apiedit/phase3/includes/
This was done months ago, forgot about this bug.